Cellular basis of immunity Flashcards

Question

Types of lymphocytes?

Answer 1

All key in adaptive immunity B-lymphocyte/Bcell - express antibodies as B cell receptors Helper T lymphocytes Cytotoxic T lymphocyte Natural killer T cell T-lymphocytes express T cell receptors

Answer 2

Have receptors specific for particular pathogen molecules proliferate Clonal selection and expansion forms the basis of protective immunity and immunological memory through which the body is protected against future attack

Answer 3

Antigen receptors and antigens Cytokines/chemokines and their receptors Cell-cell interactions

Answer 4

``` Cytoplasm Intracellular vesicles of cells Interstitial spaces Blood or lymph Epithelial cells ```

Answer 5

Skin Cuts or burns Main portals of entry is the mucosal epithelia of the gastrointestinal respiratory and urogenital tracts

Answer 6

The recognition and elimination/containment of infectious organisms Most front line defences provided by the innate Consists of molecules and cells that distinguish host cells from those of infectious agents by recognising conserved constituents of microorganisms Activated within hours of contact and efficacy not significantly increased by previous exposure

Answer 7

Cells of the innate and adaptive immune systems are derived from the pluripotent hematopoietic stem cell The HSC divides to replace itself and produce a progenitor cell with the potential to give rise to all of the hematopoietic line ashes by generating further progenitor cells committed to progressively narrower ranges of differentiated fates

Answer 8

erythrocytes and to megakaryocytic which shed fragments that form the platelets that initiate blood clotting

Answer 9

Phagocytic and inflammatory cells of innate immunity

Answer 10

T and B cells of adaptive immunity and to natural killer (NK) cells which are specialised cytotoxic cells Killer cells count as innate as don't require activation

Answer 11

SCF = stem cell factor TPO =Thrombopoietin (platelet production) EPO = Erythropoietin (erythrocyte production)

Answer 12

Basophils, mast cells and eosinophils Mast cells have a sentinel role, whilst basophils and eosinophils are circulating cells recruited from the bloodstream Whereas neutrophils destroy internalised micro organisms these cells typically provide immune defence against pathogens too large to be internalised On activation they release the contents of their cytotoxic granules to the exterior creating an environment hostile to an invading organism or directly killing it They also release histamines that mediate allergic and inflammatory responses such as coughing sneezing and vomiting These expulsive responses may be mechanisms that are evolved to expel parasites All 4 are known as the granulocytes

Answer 13

Ilya Mechnikov (1898)

Answer 14

neutrophils and macrophages which are effector cells, specialised to internalise and destroy micro organisms, and dendritic cells which internalise micro organisms for presentation to T lymphocytes of the adaptive immune system

Answer 15

Front line effector cells of innate immunity After differentiation they circulate for a few hours before entering tissues to engulf microorganisms and destroy them via microbicidal products stored in vesicles

Answer 16

Long lived cells that provide immune surveillance They are derived from monocytes that circulate in the blood, differentiating as they leave the blood stream Like neutrophils they ingest and destroy micro organisms

Answer 17

Are involved in the induction of adaptive immunity As immature cells they operate as phagocytes but rather than destroying the micro organisms they ingest their function is to display the ingested particles on their surface for recognition by T lymphocytes

Answer 18

Scavenger receptors - recognise particles released by dead or damaged tissues Complement receptors and antibody receptors Similar on dendritic cells

Answer 19

Directly through recognition of micro organisms or indirectly through recognition by cells of the adaptive immune system that then activate the innate immune defences This is done as a lymphocyte of the adaptive immune system produces antibodies whose variable regions recognise a surface component of the bacterium A non variable region of the antibody is then recognised by a receptor of the phagocyte which in turn is activated engulf it. In this way, bacteria that have masked the conserved components can be recognised and destroyed by the innate immune system

Answer 20

A general term for soluble components of the immune system that coat micro organisms and stimulate uptake by phagocytes

Answer 21

On activation by microbial surfaces they release cytokines and chemokines that amplify the response to infection Cytokines and chemokines are signalling molecules. They increase the permeability of blood vessels and recruit additional cells and molecules of the immune system to sites of infection - the inflammatory response Hence they activate the adaptive immune response

Answer 22

From a macrophage Recruits neutrophils, basophils and T cells to site of infection

Answer 23

Fluid matrices contain antibacterial peptides and toxic proteins that are constitutively secreted and further induced in response to cell wall components such as lipopolysaccharide B-defensins in lung and skin a - defensives in paneth cells of the intestinal tract Lysozyme in fluids bathing the cornea Cathelicidins (another group of antimicrobial defensins) are produced by activated neutrophils and epithelial cells in addition to antimicrobial activity they trigger signaling through the formyl peptide receptor an innate immune recognition element thereby aiding recruitment of neutrophils to inflammatory sites

Answer 24

powerful chemoattractants and activators of neutrophils Derived from BH2 terminal extensions of newly synthesised polypeptides fMLP directs the transport of secreted proteins the possess NH2 terminal signal peptides Cleaved by a signal peptidase following polypeptide transport and released into the extracellular space

Answer 25

powerful chemoattractants and activators of neutrophils Derived from BH2 terminal extensions of newly synthesised polypeptides fMLP directs the transport of secreted proteins the possess NH2 terminal signal peptides Cleaved by a signal peptidase following polypeptide transport and released into the extracellular space

Answer 26

neutrophils are attracted to bacterial chemical products like the peptide fMLP

Answer 27

Memory T cells monitor keep the tissues of the body under surveillance If they detect no antigen they return to circulation via the lymphatic system If there is an antigen it is processed by antigen presenting cell, and presented as MHC peptide complexes This activates memory T cells Which release cytokines such as TNF-a which act on local blood vessels TNF-a activates the vascular endothelium Loosens gaps in them so more blood leaks out, swelling occurs and looks more red due to RBC The activated endothelium also releases adhesion molecules that allows phagocytes out the blood vessel Takes 1-3 days The phagocytes uptake the antigen and also can present it Memory and effector T cells also leave the vessel

Answer 28

Cytokine receptor consist of 2 chains Each having an extracellular binding domain An a intracellular binding domain which has JAKs kinases on Without cytokines these 2 receptors are not associated Cytokines stabilise the heterodimer bringing them together, including the 2 JAK kinases The JAK kinases can then phosphorylate the cytoplasmic tails STAT molecules then bind to the chains at the bottom of the receptors which get phosphorylated by the JAKs The STAT molecules can now dimerise and migrate into the nucleus where they can directly activate gene transcription

Answer 29

Blood vessel endothelium at sites of infection expresses selectin molecules (P-selectin and E-selectin) the selectins are triggered by cytokines released by sites of inflammation Leukocytes such as neutrophils express the ligand for these selections in the form os s-Lex These creates a weak bond with the selectins and the neutrophils rolls along the blood vessel forming and breaking bonds These neutrophils will find somewhere they can squeeze for the endothelial cells out of the blood vessel Only happens in veins

Answer 30

Immediate response minutes to hours Semi specific, recognition through invariant specifc receptors (PAMP) Includes Granulocytes DC/Mono/Mac NK cells TLR/NLR/RLH Cytokines Chemokines Antimicrobial molecules& complement No memory

Answer 31

Functional 4-7 days after exposure Specific through epitope specific receptors (TCR, lg) Includes T cells/B cells DC TCR/BCR Antibodies Cytokines Chemokines Memory

Answer 32

Neutrophils followed by lymphocytes

Answer 33

Neutrophils

Answer 34

Lysozyme - released in fluids of cornea, saliva and gut (Paneth cells) Breaks down peptidoglycan, a component of the bacterial cell wall Phospholipase A2 - breaks down phospholipids in cell membrane of bacteria Antimicrobial peptides - Defensins - (alpha-defensins in Paneth cells of the intestinal tract and beta-defensins in lung and skin) – disturb the cell membrane of bacteria and fungi Cathelicidins (another group of antimicrobial defensins) are produced by activated neutrophils and epithelial cells Histatins (oral cavity, active against fungi) Lecticidins (creates a pore in microbial cell membranes) Complement: exists in fluids and blood: capable of direct killing of pathogens through membrane attack complex (MAC) also potentiates phagocytosis and the recruitment of other inflammatory mediators

Answer 35

Small proteins that are synthesised by the liver, tissue macrophages, blood monocytes and epithelial cells of the genitourinary system and gastrointestinal tract They circulate the blood as inactive precursors Can diffuse into tissues Capable of direct killing of pathogens through membrane attack complex Potentiaites phagocytosis Potentiates the recruitment of other inflammatory mediators

Answer 36

Is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane. Its spontaneous and low level activation If deposited onto pathogen = activation If deposited into host cell = inhibited

Answer 37

Cleaves C5 into: C5a: potent anaphylotoxin C5b: initiates Membrane attack complex

Answer 38

or terminal complement complex (TCC) is a structure typically formed on the surface of pathogen cell membranes as a result of the activation of the host's complement system, and as such is one of the effector proteins of the immune system. In order to permeabilize both the bacterial outer and inner membrane and thus kill a bacterium,

Answer 39

Phagocytosis occurs mostly in neutrophils and in monocytes/macrophages/dendritic cells

Answer 40

The phagolysosome is matured through sequential fusion with endosomes and lysosomes and becomes a very specialised intracellular compartment The bug is digested and degraded Unpleasant environment for microbes

Answer 41

Microbes are recognised by phagocytic surface receptors: 1. PAMPS-PRR (Toll-likereceptors, C-type lectins, scavenger receptors) 2. Opsonization Microbe coated with complement = binds CR3-CR4 Microbe coated with antibody = antibody binds FcRecepors Recognition and subsequent signalling trigger phagocytosis

Answer 42

The phagolysosome is matured through sequential maturation with lysosomes and becomes a very specialized intracellular compartment with: Low pH (pH=4.5): mediated by a V-ATPase proton channel Accumulation of reactive oxygen species (NADPH oxidase - subunit gp91 or NOX2, and others)  oxidative stress Accumulation of nitric species (iNOS)  nitrosative stress Antimicrobial enzymes : cathelicidins, defensins, acid hydrolases, which are secreted into lumen of phagosome. Low nutrients: no sugars, no micronutrients (Fe, Cu, Zn, etc), which are pumped out of the phagosome or sequestered (lactoferrin). Phagosome maturation to phagolysosome takes 30-60 min.

Answer 43

When for example the phagasome pumps out iron which the microbe needs to live for nutrition

Answer 44

To perform antigen presentation, to degrade antigens and load them to bridge adaptive immunity

Answer 45

The phagosome is basic (pH = 8 for about 30 min) to facilitate optimal activity of elastase and catches-in G

Answer 46

Eosinophils (toxic granules): They release mitochondrial DNA against bacteria ``` They also release granules are active against parasites, such as: major basic protein (MBP) eosinophil cationic protein (ECP) eosinophil peroxidase (EPX) eosinophil-derived neurotoxin (EDN) ``` Neutrophil extracellular traps (NETS) are also used catch microbes in sticky DNA fibrils

Answer 47

Granuloma can contain microbes Coordinated response of TH1 T-cells and macrophages which creates a layer of macrophages and outer layer of T cells which walls off the pathogen Important in tuberculosis and in certain parasite infections Means we can co live with the parasite

Answer 48

The liver, gets rid of bad bacteria This is done by liver macrophages called Kupffer cells using CRig functions as a pattern recognition receptor on Kupffer cells to directly bind gram positive bacteria via LTA, CRig-LTA is required for clearance of circulating bacteria

Answer 49

Communication between all cells of the immune system Phagocytosis occurs simultaneously with release of cytokines and chemokines Complement deposition triggers phagocytosis and recruitment of other immune cells Cytokines made by macrophages and dendritic cells trigger recruitment of neutrophils and acute-phase response

Answer 50

Different PRR and cytokines  signal integration  adaptation of responses to each pathogen Each microbe activates a set of PRRs different response based on ratio of signals allows a targeting of the response to pathogen and to tissue Feedback mechanisms Once other immune cells migrate into the tissue the cytokine and chemokine milieu modulates function of innate immune cells  differential activation of macrophages and monocytes ( and perhaps other cells)

Answer 51

If its chronic can cause a degenerative or auto immune disease This is prevented by: Host cells have mechanisms to prevent activation of innate immune killing Intracellular signalling cascades triggered by PAMPS and DAMPS direct the magnitude and nature of the immune response in a tissue specific manner

Answer 52

posited that the primary function of the immune system is to sense and respond to danger in the form of signals (ATP, adenosine) derived from damaged tissue, regardless of the source of damage. Danger-Associated Molecular Patterns (DAMPS)

Answer 53

posited that lymphocyte activation is controlled by evolutionarily ancient system of germline-encoded pattern-recognition receptors (PRR) that detected conserved pathogen-associated molecular patterns (PAMPS) - predicted that PRR-PAMP interactions would induce costimulatory molecules on APCs.

Answer 54

: CYTOKINE STORMS, IMMUNE-MEDIATED DAMAGE, ALERGY, FIBROSIS

Answer 55

The adaptive immune system consist of T and B lymphocytes The T lymphocytes and immunoglobulins, and antibodies that B-lymphocytes produce can recognise an unlimited number of different targets Become effective only after a delay of 2 to 4 days on first encounter Lymphocytes and lymphocyte products specific for a given organism then persist as immune memory and are rapidly protective on re-exposure to the same infectious agent This property of the adaptive immune system forms the basis of the protective effects of vaccination

Answer 56

The ability of the body to remember an infectious agent to which it has been exposed is the basis for natural and artificial immunity against a disease Vaccination initiates a primary immune response, generating memory cells without making the person ill Later, if the same or very similar pathogens invade the body, specific memory cells already exist They recognise the agent and produce massive number of lymphocytes and immunoglobulins that overwhelm the invaders

Answer 57

Adaptive immune responses are mediated by lymphocytes of the lymphoid lineage which fall into two major classes: T lymphocytes - kill virus-infected and cancerous cells (CD8+ T cells/cytotoxic T lymphocytes or CTLs or, activate other cells of the immune system (CD4+ helper T cells) B lymphocytes - secrete immunoglobulins Natural killer cells -capable of killing virus-infected or cancer cells immediately without prior activation and without clonal expansion They are generally regarded as part of the innate immune system (because they don’t require prior activation) Activation occurs via binding of activating receptors to surface molecules produced by cell damage e.g. cancer or that are encoded by infecting viruses

Answer 58

Any molecules or parts of molecules recognised by the variable antigen receptors of lymphocytes are known as antigens

Answer 59

Mature lymphocytes that have not yet encountered antigen are known as naïve lymphocytes Differentiation into effector cells is stimulated by encounter with antigen and is preceded with a vigorous proliferation that selectively expands the numbers of those lymphocytes with receptors specific for the inducing antigen This is known as clonal selection of antigen- specific lymphocytes

Answer 60

The critical interactions between activated dendritic cells and lymphocytes occurs in lymphoid tissues Lymphocytes enter lymphoid tissues from the bloodstream Return to the bloodstream through the lymph if they are not activated Migration through lymphoid tissues, and cellular interactions, are guided and controlled by adhesive cell surface molecules whose expression is regulated by cytokines and chemokines

Answer 61

``` T lymphocytes recognise antigens by means of T cell receptors generated during their differentiation - they interact with APCs (antigen- presenting cells - DC, macrophages and B cells) via complementary ligands ``` Each individual lymphocyte expresses an antigen receptor of only one specificity, but the total population of lymphocytes in any given individual is collectively capable of recognising virtually any antigen

Answer 62

Clusters of differentiation

Answer 63

Marker of helper T cells Is a co receptor for MHC call II molecules These co-receptors play an important part in signal tranduction on antigen binding by T cells

Answer 64

Marker of cytotoxic T cells Co receptor for MHC call I molecules These co-receptors play an important part in signal tranduction on antigen binding by T cells

Answer 65

Dendritic cells of the innate immune system play a crucial role in activating adaptive immunity Begin life as phagocytes but when activated by conserved components of micro-organisms, or by inflammatory cytokines released by macrophages, become dedicated to displaying components of ingested micro-organisms for recognition by naïve T lymphocytes and subsequent differentiation of naïve T lymphocytes into effector T cells Especially numerous in epithelia and at mucosal surfaces Langerhans cells first recognised in the skin in the 19th century. They are a subset of dendritic cells that reside in the keratinised epidermis for several months Second population of skin-resident dendritic cells is found in the dermal layer - known as dermal dendritic cells or interstitial dendritic cells In mucosal epithelium of the gut, dendritic cells are concentrated at specialised sites of antigen collection that overlie lymphoid tissues Some have specialised surface properties that enable them to extend their long dendritic processes between the cells of the epithelium and into the lumen to sample antigens These cells are directly exposed to ingested antigens and to commensal bacteria as well as invading pathogens These cells have a specialised role in preventing inflammatory responses to harmless gut residents

Answer 66

deliver antigen from the lumen of the gut to the underlying tissue where dendritic cells cluster

Answer 67

A dendritic cell displays a component of a micro-organism for recognition by a T lymphocyte bearing a receptor for that component. This stimulates it to proliferate and differentiate into an effector cell. When the effector cell recognises the same antigen displayed on the surface of a B lymphocyte, the T cell activates the B lymphocyte, which in turn proliferates and secretes antibodies that recognise the micro-organism

Answer 68

Unlike B cells whose surface immunoglobulin molecules are adapted to serve as antigen receptors, T cells are unable to interact directly with intact antigen and so must interact with other cells of the immune system T cells are focused on their target cells by cell surface proteins known as MHC molecules because they are encoded in the major histocompatibility complex (MHC) MHC molecules carry fragments of antigen, usually peptide fragments of proteins, from internal compartments of the target cell to the cell surface and display them for recognition by the T cell All naïve T cells are activated by antigen fragments displayed on MHC molecules on the surface of dendritic cells, and after differentiation into effector cells they are triggered to kill or activate cells displaying the same complex of MHC and antigen

Answer 69

Chromosomal region containing genes that encode cell surface proteins that regulate interactions among cells of the immune system During transplant the more similar they are the longer it will take for the body to reject the new organ There is class I molecules (Activate CD8 T cell) and class II molecules (Activate CD4 T cell) These monitor different internal compartments of cells and are recognised bu distinct classes of T cells

Answer 70

The cytoplasm All viruses and some important bacterial pathogens replicate in the cytoplasm Vesicles of the endosomal/lysosomal pathway Contain internalised antigens derived from extracellular pathogens In the specialised case of macrophages, vesicles may harbour bacteria and some fungi (e.g. Cryptococcus) adapted to survive phagocytosis The cytoplasm is monitored by MHC class I molecules Vesicular compartments are monitored by MHC class II molecules

Answer 71

MHC class I molecules are expressed on all nucleated cells (not RBC) including APCs and bind peptides generated by cytoplasmic proteases from cytoplasmic proteins Their critical role is to display antigens derived from pathogens that replicate in the cytoplasm, and antigen displayed on MHC class I molecules is recognised by cytotoxic T cells, which kill the infected cells This system ensures the destruction of cells in which cytoplasmic pathogens are replicating and is believed to be essential for the elimination of some of these pathogens

Answer 72

A specialised white blood cell responsible for eliminating unwanted body cells (eg. cancer cells) for example killing a cell infected with influenza virus

Answer 73

``` Peptide fragments of pathogens, such as viruses, that replicate in the cytoplasm compartments of cells are carried to the cell surface by MHC class I molecules and are recognised by cytotoxic T cells forming an immune-synapse, outer ring is an adhesion ring and the inner is a signalling zone and secretory zone ``` Upon activation, CD8 T cells produce: 1. Perforins - proteins that form pores in the membrane of target cells 2. Granzymes - proteases that induce programmed cell death on entry into target cells

Answer 74

MHC class II molecules are normally expressed only on cells of the immune system, and in particular on professional APCs (B cells, macrophages and dendritic cells) They bind to peptides generated from internalised antigen in the endosomal compartments of cells Antigen derived from internalised micro-organisms by lysosomal proteases and displayed by MHC class II molecules on dendritic cells is recognised by naïve T helper cells at the initiation of immune responses

Answer 75

The 2 chains of it form in the endoplasmic reticulum An invariant chains binds to the peptide grove formed by the 2 chains Preventing unwanted peptides in the ER from binding The invariant chains takes it through the ER and Golgi apparatus via a vesicle Proteases are released inside the vesicle cleaving the invariant chain in 2 places leaving the CLIP peptide bound to the MHC class II molecule Engulfed proteins or pathogens that are degaded in the vesicle can't mind on to MHC class II as it's blocked by CLIP HLADM allows the CLIP to be removed, its present in the vesicle and acts as a catalyst The pathogen peptides can now bind and the vesicle is taken to the cell surface to present as as an antigen

Answer 76

They recognise antigen bound by MHC class II molecules on the surface of dendritic cells

Answer 77

``` Helper T cells recognise fragments of a pathogen that has been internalised by macrophages and have undergone proteolytic digestion to generate fragments that are carried to the cell surface by MHC class II molecules. ``` The helper cell is then stimulated to activate the macrophage to destroy the internalised pathogen. This is particularly important for defense against bacteria that are able to grow in the internal vesicles of macrophages Helper T cell tells the macrophage via cytokines that what its doing is correct

Answer 78

``` B cells internalise antigens bound to their surface immunoglobulin and deliver them to the endosomal compartments of the cell where they are digested into fragments. The antigen fragments then bind to MHC class II molecules which carry them to the cell surface where they are recognised by helper T cells, which then activate the B cell to proliferate and differentiate into an antibody- secreting plasma cell ```

Answer 79

Coreceptor from Tcell receptor binding to MHC

Answer 80

There is TH1 and TH2 which release different cytokines which have different effects (picture in folder)

Answer 81

Enhance and sustain signal delivered by the MHC-antigen T cell receptor interaction (photo in folder)

Answer 82

Professional antigen presenting cells present either MHC moelcules and co stimulator molecules such as CD80(B7.1) When a complex is formed with the T cell signals are sent both ways, it tells the antigen presenting cell to produce more co stimulator pairs, and the T cell is induced to form pairs for the new co-stimulator pairs which can then form ligand making the connection stronger with the T cell This then stimulates another co stimulator that is required when bound for full activation of the T cell

Answer 83

Pathogens manages to get through first layer of skin (through epidermis into dermis) The bacteria establish an infection here Phagocytic cells such as neutrophils and macrophages engulf the pathogen Dendritic cells engulf as well and are stimulated by binding pathogens to leave the site of infection and migrate to a lmpyh vessel where the are drained into a lymph node In the lymph node T cells are activated by the antigen presented on the dendritic cells and in turn activate B cells to release antibody Effector T cells and antibody return to circulation They return to the site of infection as inflammatory mediators have caused changes in the blood vessel endothelium CD4 T cells activate macrophages to become more cytotoxic antibody recruits complements of lysed bacteria directly and to opsonise them by inducing there uptake by phagocytes In the case of a virus activated CD8 cells would kill any infected cells present

Answer 84

More susceptible to uptake by phagocytosis

Answer 85

Host proteins produced in response to the presence of foreign molecules in the body Synthesised primarily by plasma cells (lymphoid lineage) and are components of the adaptive immune system Circulate throughout the blood and lymph where they bind to foreign antigens Antibody-antigen complexes are removed from circulation primarily through phagocytosis by macrophages

Answer 86

The lymphocytes of any individual collectively express a large number of different receptors Some cells bear receptors that recognise self-antigens. While still immature, they are eliminated This process of clonal deletion is a critical mechanism for ensuring self-tolerance Once mature, lymphocytes activated by recognition of foreign antigen differentiate into effector or memory cells through a process of clonal expansion This is the mechanism for antigen-specific immune responses and immune memory

Answer 87

The mechanism through which self-tolerance is established differs between T cells and B cells An immature B cell in the bone marrow expresses membrane Ig antibody together with Iga and Igb chains as the B cell receptor If the BCR in is engaged by self antigens present in its local environment, maturation of the B cell is arrested and it stays in the bone marrow Re-arrangement and recombination of genes encoding the BCR results in a new BCR possessing the original heavy chain but new light chain This process is known as receptor editing If the B cell is no longer auto-reactive, then it is exported to the periphery If this BCR is still auto-reactive, then it can try again for a limited time before dying (clonal deletion)

Answer 88

Germinal centres where B cells proliferate and undergo isotope switching hyper mutation Germinal centres form from dendritic cells having antibody on their surface activating antigen specific CD4 T cells which proliferate into effector cells capable of activating antigen specific B cells Once activated it proliferates to form a primary focus for antigen specific B cells B cells from the primary focus migrate to nearby follicles whilst other B cells stay in the local area secreting antibody B cells that enter to follicle proceed to proliferate rapidly under this time they also undergo somatic mutation to introduce new variation into the B cell receptor The receptors are tested with their ability to bind to antigen those that fail to compete die

Answer 89

Large family of glycoproteins Share key structural and functional features Functional - able to bind both to antigens and to specialised cells or proteins of the immune system Structural - composed of one or more copies of a characteristic unit that form a Y shape So any molecules or parts of molecules recognised by the variable antigen receptors of lymphocytes are known as antigens

Answer 90

The specific region of the antigen bound by the variable region of an immunoglobulin

Answer 91

The antigen binding region of an antibody

Answer 92

Affinity is the measure of the strength of the binding of an antigen by an antibody Antibody binding to antigen is non-covalent and reversible The affinity of an antibody (Ab) for an antigen (Ag) is related to the ratio of the rates of the forward reaction for formation of the complex to back reaction for decay of the complex Like a reversible reaction in chemistry A level

Answer 93

Fab 1 Fab 11 Intact Fc 111

Answer 94

F(ab)2 Fc fragments

Answer 95

Heavy chain is top part of arm of Y Light chain is lower part of arm of Y Each Y contains four polypeptides Two identical heavy chains (55kDa each) Two identical light chains (22kDa each) The four polypeptide chains are held together by disulphide bridges and non-covalent bonds The two domains that carry the antigen binding sites are known as Fab fragments (fragment having the antigen binding site) (the 2 arms) (antigen binds at the end of the arm) The third domain is known as the Fc fragment (the fragment that crystallizes) (the base) Hinge region in the middle of the arms aids movement ``` The ability to bind antigen is determined by the N-terminal domains. These differ considerably between antibodies of differing specificities and are therefore termed ‘variable’ or ‘V’ domains - the end bits of each of the arms ``` Top part of the base of the Y is where complement binding happens Bottom bit of the base of the Y is where binding to Fc receptors happens

Answer 96

``` VH is top bit of the top arm of the Y, VL is the bottom bit of the top of the Y arm Sequence analysis of amino acids of VH and VL regions reveals small regions of hyper-variability within four conserved framework regions (FR1, FR2, FR3 and FR4) ``` In the 3-dimensional structure, the hyper-variable regions form loops that combine together to form the principal antigen-binding surfaces These surfaces are called the complementarity determining regions or CDRs (CDR1, CDR2 and CDR3)

Answer 97

There are five main classes of antibody in serum IgG, IgM, IgA, IgE and IgD The five classes are divided on the basis of the number of Y-like units and the type of heavy chain polypeptide they contain (y, u, a, e and delta ) Greek symbols and associate same order as ones above While there are five different types of heavy chains, there are only two light chains (k or L) Greek again One light chain always associates with one heavy chain, so the number of light chains always equals the number of heavy chains There's 2 heavy chains and 2 light chains per antibody

Answer 98

In humans, the IgG class has four sub-classes (G = gamma) IgG1, IgG2, IgG3 and IgG4 These have y1, y2, y3 and y4 heavy chains The IgA class has two sub-classes IgA1 and IgA2 These have a1 and a2 chains respectively

Answer 99

Holds more than 1 antibody together

Answer 100

In double antibodys

Answer 101

IgA is the most prevalent immunoglobulin in mucosal secretions Binds to antigens and prevents the uptake of bacteria and toxins Epithelial cells in the intestine mediate the transfer of dimeric serum IgA to the intestinal lumen via the polymeric Ig receptor IgA dimer with J chain attached binds to the polymeric Ig receptor, a transmembrane protein expressed at the basal surface of epithelial cells of the gut, airways and various secretory glands Binding of IgA induces transcytosis of the polymeric Ig receptor Complex is delivered to the apical surface of the epithelial cell and into the lumen Proteases cleave the pIgR near the membrane, releasing the majority of the extracellular domain still bound to IgA dimer The ‘secretory component’ protects IgA from proteases present in mucus and anchors IgA at the desired location After opsonisation with IgA, the receptor Fca/mR mediates the uptake of organisms by macrophages and dendritic cells A second receptor FcaRI mediates uptake by neutrophils IgA deficiency is a common immunodeficiency in humans IgM can compensate for IgA deficiency by also binding to pIgR IgM opsonised organisms are phagocytosed via Fca/uR Activating Fc receptors signal through ITAMs

Answer 102

Antigen receptors, Fc receptors and some of the activating receptors of natural killer cells signal via a common mechanism that is dependent on a conserved amino-acid sequence motif This is known as the immunoreceptor tyrosine-based activation motif The ITAM contains two precisely spaced tyrosines within a consensus sequence When phosphorylated, the tyrosine residues provide a binding site for one or two closely related intracellular tyrosine kinases Syk in most immune cells ZAP-70 in T cells These have tandem SH2 (Src Homology 2) domains spaced at exactly the right distance apart to dock onto the two phosphotyrosines, and that activate signaling events downstream of the receptor

Answer 103

The surface immunoglobulin (Ig) that serves as the B cell receptor for antigen brings the receptor into proximity with a Src- family tyrosine kinase, which is held in the plasma membrane by a lipid tail and phosphorylates ITAM tyrosines in the receptor Iga and IgB chains This creates a binding site for Syk, which binds to the doubly phosphorylated ITAM sequence Once bound, Syk becomes activated by tyrosine phosphorylation and it then phosphorylates other signaling proteins that ultimately bring about changes in the behaviour of the cell e.g. antibody production

Answer 104

The two most widely recognised mechanisms of antibody- mediated toxicity are: 1. Antibody-dependent cell-mediated cytotoxicity (ADCC) Antibody attracts cytotoxic cells by means of their Fc receptors 2. Complement-mediated cytotoxicity (CMC) Antibody binding results in the fixation of complement onto the target cell

Answer 105

It requires triggering of specific receptors on the phagocyte Fc receptors that bind antibody coated bacteria are one of the receptors capable of triggering phagocytosis engulfing it and forming a phagosome Lysosomes move in to degrade the content in the phagosome

Answer 106

The complement system, also known as complement, consists of about 30 serum and membrane proteins that can mediate a variety of immune reactions including: Triggering inflammatory responses Attraction of phagocytes to sites of inflammation Degradation of membranes or virus envelopes Stimulation of antibody production

Answer 107

The active components of complement are generated from inactive precursors by a cascade of proteolytic reactions These are triggered through 3 different pathways: The LECTIN pathway (recognition of carbohydrate moieties e.g. by collectins such as mannose-binding lectin) 2. The CLASSICAL pathway (antibody binding to antigen in immune complexes) The ALTERNATIVE pathway (directly at microbial cell surfaces) Activation of complement by any one of the pathways initiates a cascade of cleavages in which each component in the pathway is cleaved into two fragments: The small fragment (a fragment) The big fragment (b fragment) The b fragment forms a subunit of the protease complex mediating the next cleavage in the pathway The reactions can be divided into early events, in which the components are not the same for the same three pathways and late events, in which they are identical

Answer 108

The function of the early events is to generate two functionally equivalent forms of a protease, known as C3 convertase C3 convertase then initiates the late events to produce the effector components of complement C3 convertase covalently attaches to the cell surface at which the complement activation was initiated Cleavage of complement component C3 leads to effector activation In this way, the effects of complement activation are confined to the infectious organism that triggered

Answer 109

Pentraxins = Pentameric serum proteins that participate in innate immunity and can also activate the Classical pathway of complement Antibody binds, C1r is activated by C1q C1r then cleaves and activates C1s C1s cleaves C4 C4b attaches to cell surface C2 binds to C2 binds to C4b C1s cleaves C2 bound to C4b producing C3 convert C4bC2n and C3bBb conertases cleave C3 which provides C3a and C3b which are the effector actions, is an amplification loop for the alternative pathway as well

Answer 110

The epithelium of the respiratory tract is lubricated by a layer of phospholipids and proteins known as surfactants ``` Two of these, Surfactant Protein-A (SP-A) and Surfactant Protein-D (SP-D) are Collectins and function as opsonins, coating microorganisms (e.g. Pneumocystis in AIDs patients - Lecture 8) and stimulating uptake by phagocytes ``` The Collectin family also includes Mannose-Binding Lectin (MBL) - binds to mannose-containing carbohydrates on surface of viruses, bacteria and fungi Ficolins bind to N-acetylglucosamine which are polysaccharides outside of microorganisms Each polypeptide chain of the collectin family of proteins consists of an amino-terminal cysteine-rich region followed by a collagen-like region, an -helical neck region and a carboxy-terminal globular domain (a C-type lectin known as the carbohydrate recognition domain [CRD]) The polypeptide chains trimerise Both Mannose Binding Lectin and Surfuctant Protein-A are hexameric structures. The multiple arrays of CRDs give high affinity binding to polysaccharide ligands in microbial cell walls Particle recognition is translated into immune action: 1. By phagocytes, which are stimulated to internalise bound microorganisms or, 2. By conformational changes in the collectin that activate pre-bound protease subunits and initiate the complement cascade

Answer 111

MASP = Mannose binding lectin associated serine protease MASp-2 cleaves C4 C4b attaches to cell surface C2 binds to C4b MASP-2 cleaves C2 bound to C4b Forming C3 convertase C4bC2n and C3bBb conertases cleave C3 which provides C3a and C3b which are the effector actions, amplifies alternative pathway

Answer 112

C3b binds to microbial surface B binds to C3b D cleaves B bound to C3b forming C3 converts C4bC2n and C3bBb conertases cleave C3 which provides C3a and C3b which are the effector actions Amplifies alternative pathway

Answer 113

peptide mediators of inflammation, phagocyte recruitment

Answer 114

Binds to complement receptors on phagocytes Opsonization of pathogens Removal of immune complexes Can also results in terminal complement components C5b, C6, C7, C8, C9, which aid the membrane attack complex, lysis of certain pathogens and cells C3b + C3 convertase → C5 convertase C5 convertase + C5 → C5a + C5b C5b + C6 + C7 + C8 + C9 ⇢ MAC

Answer 115

Undesirable reactions produced by the 'normal' immune response Can be an allergy or auto-immunity allergy = reacting to something not normally in the body Auto-immunity - reacting to stuff in our body

Answer 116

``` Type-I - IgE Causes degranulation of mast cells Allergy Asthma ``` ``` Type II - IgG Can recruit complement and attack things such as RBC Autoimmune haemolytic anemia ``` ``` Type III - IgG Binds to Fc receptor and recruits macrophages and neutrophils to the cell Rheumatoid arthritis ``` ``` Type -IV Doesn't use antibodies Cellular effectors Multiple sclerosis ``` Old system they are all mixed up in fact

Answer 117

• Excessive immune responses to harmless antigens (allergens) - Most allergic reactions are due to IgE-mediated responses • ~40% of adults show an allergic response to least one environmental allergen: Atopy: individuals that have a predisposition to become IgE-sensitized to allergens No major common characteristics between allergens has been identified! • Airborne allergens – small, soluble proteins (some with protease activity)

Answer 118

``` Anaphylaxis Acute urticaria Allergic rhinitis Asthma Food allergy ```

Answer 119

Airway hypersensitivity | Lung epithelium inflammation, smooth muscle contraction

Answer 120

Which CD4+ Th subset it is In allergy think its highly a Th2 mediated response can be termed Type 2 immunity

Answer 121

IgE production that is specific to the allergen after CD4+ Th2 has stimulated a B cell

Answer 122

Can express tight junction proteins allowing interaction with epithelium Epithelial cells can secrete factors that trigger DC activation: Instructive cytokines DAMPS - damage associated molecular pattern

Answer 123

Mast cells: abundant in mucosal tissues (lung, gut) and connective tissues (e.g. surrounding blood vessels) Th2 tells B cell via Type 2 cytokines (IL - 4, IL - 5, IL - 13)to class switch IgE antibody, which forms plasma cells which take the antibody to the Fc receptors on mast cells that causes degranulation when stimulated by the allergen Most IgE is cell bound (on FcεR) not in body fluids (unlike other antibodies)

Answer 124

``` Histamines • Proteases • Enzymes • Cytokines • Prostaglandins • Leukotrienes ``` In intestines causes fluid secretion and peristalsis that can case GI contents expulsion through diarrhoea or vomiting Can decrease airway size increasing mucus Increase blood flow and permeability - causing anaphylactic shock

Answer 125

Circulating rather than in tissue Originate from bone marrow progenitors and are continually circulating In health (% of circulating leukocytes): Eosinophils ~ 2-6% Basophils ~ 0.4% (very rare!) Recruited to tissues via chemokines to sites of inflammation… Activated by type-2 cytokines (especially IL-5), complement and antibodies Release enzymes, toxic proteins, cytokines chemokines and leukotrienes Characteristic feature of allergic disease (yet role is unclear)

Answer 126

PEFR = peak expiratory flow rate = lung function 30 minutes huge dip in function due to mast cells but returns to normal in another 30 minutes In late phase will dip not as steep around 8 hours

Answer 127

Too much mucus made: Goblet cell hyperplasia Airway smooth muscle: Hyperplasia and hypertrophy ECM deposition: deposition of collagen

Answer 128

Antihistamines Target H1 receptor Adrenaline Anaphylactic reactions, e.g. reforms endothelial tight junctions and relaxes smooth muscle. Inhaled bronchodilators Act on β-adrenergic receptors to relax constricted muscle ``` Immunosuppressive drugs (general anti-inflammatories) – corticosteroids Suppress immune inflammation (can be given via inhalation) ```

Answer 129

Antibody therapies: Omalizumab (anti-IgE) Reduces asthma symptoms; • Allows for a reduction in inhaled corticosteroid (ICS) dose Mepolizumab & Reslizumab (anti-IL-5 antibodies) • Some evidence of efficacy, but only with patients where eosinophils are dominant (prednisone-dependent eosinophilic asthma). Duplimab (anti-IL-4Rα – receptor for IL-4 and IL-13) • Effective at controlling asthma with reduction in corticosteroid dose in mild to severe asthma patients that have high eosinophil blood count. Low dose allergen therapies (allergen de-sensitization): • Injection of low doses of allergen (that escalate). • Mechanism unclear, though likely to involve Tregs and skewing toward IgG.

Answer 130

Autoimmune disorders high in Western culture Much cleaner Could be due to microbiota

Answer 131

Common to the pathogen is this lecture it is bacteria Pathogen associated Molecular patterns (PAMPS) The innate system is pre coded to recognise a limited repertoire of molecules This enables it to respond quickly, but to provide a low level response It kills by complement and interactions with phagocytes

Answer 132

In all pathways the first step is the recognition of microbial components: Alternative pathway: Recognised molecule - Spontaneous activation but various cell surface molecules play a role Classical pathway: Recognised molecule - Bound IgM or IgG, so relies on antibodies and is far more effective in individuals who have been previously exposed Lectin pathway: Recognised molecule - Carbohydrates such as mannose or N-acetyl glucosamine

Answer 133

C3 converts C3 converts covalently attaches to the cell surface at which the complement activation was initiated Turns into C3a (Inflammation - binding to receptors on mast cells, causing them to release histamine) and C3b (opsonization and phagocytosis) In this way, the effects of complement activation are confined to the infectious organism

Answer 134

C3B forms part of the C5b convertase helping to later form the membrane attack complex which causes lysis of the microbe C5b also produces C5a which causes inflammation

Answer 135

The Gram-positive cell wall tends to be thicker and more robust than the Gram negative cell wall The MAC is much more active towards Gram-negative than gram positive bacteria Ion influx and efflux causes the cell to lyse

Answer 136

Can see that deficiency in being able to produce certain types of complement results in not being Protected against certain types of bacteria

Answer 137

bacteria coated with antibodies are recognised by antibody receptors (Fc receptors) Bactiera coated with C3b are recognised by C3b receptors

Answer 138

PAMPS are recognised Pattern recognition receptors such as Toll-like receptor

Answer 139

Extracellular domain - ligand recognition Intracellular domain - signalling (dimerisation is essential for signalling) so TL1/2 would be a heterodimer and TL5/5 would be homodimer

Answer 140

Activation of phagocytes which leads to: Cytokine and chemokine production Ingestion and killing

Answer 141

Recognition of bacteria molecule by TLR Dimerisation of the TLR Signalling and inflammatory responses

Answer 142

Recognises antigens that are unique to an individual pathogen It takes time to develop and mature but can provide a very powerful protective response Normally recognises proteins or polysaccharides

Answer 143

Protein within the cytosol: Processed by the proteasome generates peptides Go to endoplasmic reticulum where become processed with MHC class 1 to form a complex which is recognises by CD8+ T cells Activated CD8 T cels kill host cells infected with bacteria by releasing cytotoxins such as perforin, granzymes and granulysin ``` Protein taken up into the phagosome: Endocytosis of extracellular protein in it's vesicle it forms a complex with with MHC class 11 from the ER, this complex is presented on the cell surface and recognised by CD4+ T cells ``` CD4+ T cells releases different cytokines that result in inflammation, macrophage activation, antibody response

Answer 144

Tuberculosis Salmonellosis listeriosis meliondosis

Answer 145

Clumps the bacteria so cleared better by phagocytes Its triggered by antibodies

Answer 146

Antibodies bound to bacteria promote complement binding and complement activation by the classical pathway Complement can now effect them

Answer 147

Antibodies can make it easier for phagocytes to uptake bacteria

Answer 148

Responsible for the commonest recurring infections of humans Although usually transient, they have massive socio-economic consequences Viruses that have ‘jumped’ species barriers (zoonotic) generally cause substantially greater mortality than endemic viruses that have adapted over greater evolutionary time to their hosts Human Immunodeficiency virus from chimpanzees in Africa Ebolaviruses from bats (via bushmeat e.g. duikers) in Africa Severe Acute Respiratory Syndrome (SARS) SARS-CoV-1 coronavirus from horseshoe bats (via civets?) in China Middle East Respiratory Syndrome (MERS) MERS-CoV coronavirus from camels in Middle East Coronavirus disease 2019 (COVID-19) SARS-CoV-2 coronavirus from bats (via pangolins?) in China

Answer 149

Epidemic: classification of a disease that appears as new cases in a given human population, during a given period, at a rate that substantially exceeds what is ‘expected’, based on recent evidence An epidemic may be restricted to one locale (an outbreak), more general (an epidemic) or even global (pandemic) Pandemic: an epidemic that spreads through human populations across a large region e.g. a continent, or even worldwide

Answer 150

Exist as obligate intracellular pathogens - dependent on host proteins for replication May contain as few as 3 to 4 to up to several hundred genes expressed from single- or double-stranded RNA or DNA genomes Genomes are enclosed within capsids (coat proteins) Cytopathic (lytic) viruses e.g. poliovirus and influenza virus, lyse host cells by inducing apoptosis or autophagy Some cytopathic viruses e.g. herpes viruses can infect cells without producing infectious virions until immunity wanes or until re-activated by various physiological signals - known as latent viruses Non-cytopathic viruses e.g. hepatitis B replicate without destruction of cells

Answer 151

GP encodes Ebola virus glycoprotein (GP). Two forms: 1. Trimeric trans-membrane complex targets virus to cells via receptor binding - allows virus to introduce its contents into monocytes/macrophages leading to inflammatory cytokine dysregulation 2. Soluble dimeric form (sGP) secreted after infection – prevents neutrophil activation

Answer 152

Immune cells get caught in endless loops releasing extreme levels of cytokines - proteins within cells which cause inflammation and attracting yet more immune cells

Answer 153

Infected cells detach from blood vessels causing massive haemorrhage. Loss of blood leads to kidney and liver failure

Answer 154

Like bacteria, viruses must overcome epithelial barriers of skin and mucosa to establish infection Intestinal viruses e.g. poliovirus enter via antigen-sampling M cells Respiratory viruses e.g. influenza virus and rhinoviruses establish infection in the epithelial cells of the airways Some viruses e.g. Zika, Dengue and West Nile viruses require insect vectors for transmission Bloodborne viruses e.g. HIV and hepatitis B can invade through mucosa or epithelia following physical trauma

Answer 155

Viruses exploit specific molecules on cells as receptors for invasion While some viruses bind widely expressed surface molecules, most viruses invade using receptors with restricted tissue expression patterns e.g. HIV They are said to display TISSUE TROPISM SARS-CoV-2 (COVID-19) accesses host cells via Spike Glycoprotein S binding to angiotensin-converting enzyme 2 (ACE2) on type II alveolar cells in lungs

Answer 156

Major innate immunity is mediated via type 1 interferons*, complement and natural killer (NK) cells Major adaptive immunity is mediated via antibody and cytotoxic T lymphocytes (CTLs) Interferons are Group of proteins that induce host cell enzymes that affect transcription and translation of viral genes

Answer 157

Appearance of virus is followed rapidly by a massive expansion of virus-specific CD8 T cells CD4 T cell expansion and contraction also occurs but at a lower magnitude Neutralising antibodies are produced relatively early after acute infection with cytolytic viruses

Answer 158

Prevent viruses leaving and entering cells

Answer 159

The C1q/r/s complex couples antibody binding to the classical pathway of complement ``` Its structure is closely analogous to MBL and H-ficolin complexes with MASPs (lectin pathway) ```

Answer 160

Acquired Immune Deficiency Syndrome (AIDS) is caused by the Human Immunodeficiency Virus (HIV) HIV infects and destroys CD4+ T cells GRID (later called AIDs) first recognised clinically in US in 1980s in intravenous drug users and gay men with no apparent cause for impaired immunity but who showed symptoms of Pneumocystis carinii pneumonia (PCP) ~50,000 people infected/yr (USA) and 39+ million deaths globally since start of pandemic in 1980s 2/3 of infected people live in Sub-Saharan Africa, 1/5th in Asia Vast majority of human AIDS infections caused by HIV-1

Answer 161

yeast like fungus pneumocystis jirovecii Is opportunistic so found in healthy people lungs as well Seen in people undergoing chemotherapy

Answer 162

HIV-1 originated in southern Cameroon from a simian immunodeficiency virus (SIVcpz), a retrovirus that infects non-human primates e.g. Pan troglodytes (chimpanzee) in West-Central Africa SIVcpz introduced into humans through bushmeat activities with subsequent mutation into HIV – requires one or more high-risk transmission channels for human-to-human spread Channels absent in Africa prior to 20th Century but growth of large Colonial African cities led to societal changes such as prostitution (with increased frequency of STDs (genital ulcer diseases e.g. syphilis)) that allowed sexually transmitted infection Earliest documented case of HIV in a human in Congo in 1959 In US as early as 1966

Answer 163

gp 120 nicking glycoprotein gp 41 transmembrane glycoprotein

Answer 164

HIV-1 can cross mucosal surfaces through M cells - prevalent in tonsils and rectal epithelia It can also gain access via epithelia damaged by ulcerative infections, or by trauma or injection (i.v. drug use or blood transfusion) Vaginal epithelia lack M cells - HIV gains access via interdigitating processes on Langerhans cells Epithelial cells in the small intestine express CCR5, a chemokine receptor HIV-1 binds to CCR5 (once tethered by galactosylceramide) via the viral envelope glycoprotein gp120 and the virus is transcytosed

Answer 165

Once across mucosal epithelial barriers, HIV-1 encounters sub-epithelial dendritic cells C-type lectin receptors (CLRs) on dendritic cells bind high-mannose N-linked oligosaccharides on viral envelope glycoprotein gp120 Interaction with CLRs initiates dendritic cell migration to regional lymph nodes Once in lymph nodes, intact virus, internalised with CLRs, is re-exposed at the surface and displayed to T cells Regardless of the route of infection, the predominant site of virus replication early in disease is in the small intestine - this reflects the large number of activated T cells that express CCR5 in that organ

Answer 166

Entry of HIV into cells mediated by viral envelope glycoprotein gp120 Binds to CD4 and chemokine receptors (CCR5 or CXCR4) on host surfaces Binding with receptor leads to a conformational change in gp120 that exposes the transmembrane component of the envelope protein gp41 gp41 mediates fusion of the virus envelope with the host cell membrane

Answer 167

HIV infects cells via 2 cell surface molecules CD4 is the primary receptor for the virus, whilst the chemokine receptors CCR5 or CXCR4 act as co receptors for the viral infection of macrophages and T cells HIV binds initially to CD4 via the envelope like protein gp120, this interaction allows the uncoating of the virus and the entry of the nucleocapsid containing the viral genome The viral reverse transcriptase copies the RNA genome of HIV into double stranded DNA which integrates into the chromosomal DNA of the host In this state HIV is latent, it becomes transcripted when the host cell is activated this results in the accumulation of viral proteins as well as genome length transcripts of the virus Viral proteins assemble at the cell membrane and bud off to form a new viral particle maturation occurs once its left the cell

Answer 168

Dendritic cells translocate HIV from mucosa within 30 minutes of infection A wave of viral proliferation in lymph nodes peaks 4-7 days after infection Viremia peaks at 14 days and all lymphoid tissues are infected by 3 weeks HIV is quiescent in resting CD4 T cells, but on T cell activation, virus production is also activated and the host cell dies >99% of virus is produced by newly infected CD4 T cells ~107-108 CD4 T cells are producing virus at any given time Loss of helper activities (mainly through cytokine stimulation) means that maintenance of cytotoxic CD8 T cells is lost as is the antibody response of B cells Infection typically results in flu-like illness from days to weeks after exposure - associated with a drop of CD4 T cells in the blood The CD4-dependent antiviral cytotoxic CD8 T cell response develops and is responsible for a prolonged period of stable viremia This is known as the VIRAL SET POINT Patients are normally asymptomatic until the CD4 T cell counts decline further - infection of developing lymphocytes in the bone marrow and thymus results in failure to replace lost T cells Opportunistic infections begin when CD4 T cell counts reach levels <200/l Death then typically ensues in about 2 years Common one is crypto coccus meningitis kills 600,000 lots of them with aids each year

Answer 169

There are 3 classes of influenza viruses - A, B and C Influenza A and B are major causes of human disease Only influenza A is responsible for pandemic outbreaks Influenza A viruses are avian viruses that adapt to humans ``` The virus is spread by aerosol droplets and establishes cytolytic infections in the epithelial cells of the upper and lower respiratory tract ```

Answer 170

Influenza A is a spherical or rod- shaped enveloped virus covered with 2 spike-like glycoproteins: Trimeric hemagglutinin (HA) Tetrameric neuraminidase (NA) HA mediates binding to cell surfaces and internalisation NA cleaves sialic acid and promotes viral release from cells

Answer 171

Influenza genotypes are diverse in birds (migratory waterfowl) and express a variety of HA (H1 to H15) and NA (N1 to N9) subtypes Avian viruses prefer receptors, primarily on intestinal cells, that have the -2,3 sialic acid linkage to galactose Human viruses prefer the -2,6 linkage expressed on respiratory epithelia Pigs express both types of linkage on respiratory epithelial cells Influenza viruses enter the human population in regions where humans, pigs and waterfowl, as wells as domestic chickens, are in close proximity Pigs can be infected with both human and avian influenza, and exchange of segments between viral genomes in the pig can give rise to variants expressing novel surface proteins together with human-adapted virulence determinants

Answer 172

Antibody mediated immunity: Can bind to HA and block viral attachment Can also bind to NA protein and prevent release of new virions ``` Cell mediated immunity: CD8 T cells recognise the infected cell due to its MHC class 1 the T cell then causes cell lysis ```

Answer 173

Epidemics occur when point mutations (red dots) accumulate in surface HA (ovals) or NA (diamonds) This leads to ANTIGENIC DRIFT so that, in many previously immune individuals, HA and NA are no longer recognised by neutralizing antibodies produced in response to earlier infections Pandemics occur when avian influenza viruses and human influenza viruses infect pigs and re-assortment of the two genomes leads to the expression of avian HA or NA in a virus otherwise adapted to infect humans (ANTIGENIC SHIFT)

Answer 174

A ‘cytokine storm’ (hypercytokinemia) is the systemic expression of a healthy and vigorous immune system Caused by release of >150 inflammatory mediators (pro-inflammatory cytokines, anti-inflammatory cytokines, free radicals, coagulation factors etc.) Precise mechanisms for cytokine storms are not known, but may be caused by an exaggerated response when the immune system encounters a new and highly pathogenic invader They have the potential to do significant damage to body tissues and organs e.g. if in the lungs, large concentrations of macrophages accumulate restricting the airways Cytokine storms occur in response to a number of infectious and non-infectious agents e.g. avian influenza, adult respiratory distress syndrome (ARDS), sepsis and Ebola

Answer 175

Because they are eukaryotes, and share many similarities with mammals, antifungal drug design is difficult (cross reactivity and thus toxicity to the host). Unicellular (yeasts_ and multicellular (filamentous) organisms Ubiquitous components of terrestrial environments where they contribute to nutrient recycling Endemic mycoses = living in geographic areas with distinct natural conditions Many fungi dispersed by air borne spores that can reach terminal airspaces in the lung Although many are transmitted from the environment, fungi that cause disease can also be normal commensal microbial flora = Candida albicans Malassezia furfur and other species of this genus lives on skin = deregulated immune response associated with dandruff and may play a role in skin exacerbating skin immune pathologies

Answer 176

Fungal infection of humans

Answer 177

Developing countries are less affected by HIV-AIDS due to access to antiretroviral regimens HOWEVER MORTALITY RATES IN SUSCEPTIBLE POPULATIONS ARE VERY HIGH 3% of patients develop infection  dependent on transplant type, Candida most prevalent 30-40% mortality rate in transplant recipients in US

Answer 178

In response to microenvironmental signals of the host (changes in pH, cell density, exposure to serum and iron deprivation), the fungus switches from the yeast form to filamentous form. The ability to switch morphologies has been linked to pathogenicity. Both forms are likely to contribute to virulence: Yeast form more easily disseminated through bloodstream Filamentous form facilitates invasion and evasion of phagocytosis Mutants unable to make the dimorphic switch are commonly non-pathogenic in animal models.

Answer 179

Innate recognition of fungi is mediated by interactions with conserved cell wall constituents (glucans, mannans, galactans). PRR Dectin-1 (gene is CLEC7A) is highly expressed on the surface of dendritic cells and in lesser amounts on macrophages It has a C-type lectin carbohydrate recognition domain that mediates the recognition of beta 1,3- and 1,6-linked glucans on the surface of intact cells and zymosan (zymosan=cell wall fragments consisting of beta-glucans, mannans, mannoproteins and chitin) So Dectin-1 is essential for immune system Engagement of Dectin-1 results in tyrosine phosporylation of its cytoplasmic immunoreceptor tyrosine-based activation motif (ITAM) Syk (Il-10) and others (TNFalpha is Syk-independent) Dectin-1 acts synergistically with TLRs to induce production of inflammatory cytokines and the production of reactive oxygen species (ROS)

Answer 180

Dendritic cells and other immune cells must be able to distinguish between apoptotic particles generated by normal tissue turnover and particles that are indicative of infection The molecules mostly responsible for making this pivotal distinction are those of the family of Toll-like receptors (TLRs) Stimulation of immune cells through their TLRs leads to synthesis and secretion of proinflammatory cytokines, thereby initiating the inflammatory response that recruits both soluble immune components and immune cells from the blood TLR stimulation of dendritic cells also induces the initiation of an adaptive immune response Acts synergistically with TLRs

Answer 181

Candida expresses surface adhesins and mannoproteins that activate the alternative and lectin pathways of complement MBL is a collectin, and is one of a number of serum proteins collectively known as opsonins MASPS (Mannose-binding lectin-Associated Serine Proteases) couple collectins to the complement pathway Before ligand binding, MASPs lack protease activity. Binding of multiple carbohydrate recognition domains of MBL to the microbial cell surface leads to conformational changes in the molecule, which promotes proteolytic activation of the MASPs, which the initiate the complement cascade

Answer 182

Activation of complement + Interactions of cell wall components, such as mannoproteins and beta- glucan, with phagocyte receptors such as TLR2 and dectin-1 stimulate release of cytokines including IL-1, IL-6 and TNF. phagocytosis by neutrophils and macrophages. Phagocytosis triggers the production of appropriate innate fungal killing mechanisms Production of cytokines by activated neutrophils, together with direct interaction of neutrophils with dendritic cells* within inflammatory sites, promotes the maturation of dendritic cells, = adaptive immunity is activated.

Answer 183

non-fatal disease of skin and subcutaneous tissues high socio-economic burden frequently occurs in tropical and sub-tropical regions of America, Asia and Africa infection occurs following transcutaneous trauma (mostly farmers) chronic disease that can take decades to develop (polymorphic skin lesion) difficult to treat (antifungals, surgical debridement, with limited success)

Answer 184

Synergy and singla intergration Resulting in enhanced cytokine production protective (curative anti-microbial immunity

Answer 185

Cryptococcus is the exception in human fungal pathogens: requires a Th1 protective response and killing seems to be more dependent on macrophages than neutrophils independent of Dectin-1, since capsule hides glucan epitopes no hyphae are produced in vivo. However giant cells are produced Titan cells. Sugar capsule = invisibility cloak, harder for the body to make antibodies against sugar epitopes

Answer 186

``` Proliferating unicellular = Protoza Malaria Trypanosomes Leishmania Toxoplasma ``` ``` Non-Proliferating multicellular helminths = Metazoa Pinworm Ascaris Hookworm Ascaris Schistosomiasis Filariasis ```

Answer 187

``` Numerous development stages Numerous hosts Vertebrate and Invertebrate Many environments Inside and outside host ``` Can then lead to long term chronic infections: Immune evasion Immune modulation Immune pathology = Absence of sterilising immunity

Answer 188

Spread mainly by female Anopheles mosquitoes Obligate intracellular parasite All of the symptoms of severe malaria occur during the erythrocytic stage of infection The liver stage is clinically silent Different immune responses are required against liver and blood stages of infection Stronger immune responses develop to the blood stage of infection Precise mechanism of how malaria infection causes sudden and life-threatening complications is unclear Cerebral malaria is when it gets into the brain 15-20% case fatality rate

Answer 189

Primary host is the sandfly Numerous different species of Leishmania parasites, each of which can give rise to a different type of disease Obligate intracellular parasite that primarily invades macrophages Can result in Mucocutaneous Cutaneous

Answer 190

Extracellular parasite • Causes “sleeping sickness”

Answer 191

Too different for adaptive immune system to work on different ones as well But there are still similar themes to protective immunity

Answer 192

Neutrophil mediating killing: Neutrophil extracellular traps… (Trojan horse) Macrophage: PRR activation and take up parasites (and infected neutrophils) via phagocytosis and enter phagosome Killing: Reactive oxygen species (ROS), triggered by phagocytosis Production of nitric oxide… Induced by IFNγ (Need help from Th1 CD4+ T cells!)

Answer 193

Subversion and evasion | Sand fly salivary proteins protect against neutrophil mediated death

Answer 194

Th1 cell rather than a Th2 cell The Th1 produces IFN-y cytokines that activate M1 macrophages which produce iNOS which produces nitric oxide which kills the parasites Regulatory T cells can also suppress immunity and macrophage function The effector functions of the pathogen specific CD4+ T cells determines the outcome of disease

Answer 195

Skin and liver stage - clinically silent and no hint of acquired immunity. Symptoms appear during blood stage Rupture of iRBCs and the release of merozoites = clinical symptoms of malaria Variant surface antigens (VSA) – binding to endothelium and rossetting of RBC.. Immune responses: Th1 CD4+ T cells, NK cell secrete pro-inflammatory cytokine macrophages production of NO B cell producing antibody (blocks invasion) But VSA antigen shift – immune evasion…

Answer 196

Trypanosome population can express up to 100 VSGs at any time. And this can be shed (avoiding complement) Sophisticated immune evasion strategy…

Answer 197

CESTODE - Tapeworms, Taenia, Echinochoccus NEMATODE - Round worms, Filaria, Ascaris, Hookworm,Trichinella TREMATODE - Flat worms, Schistosomiasis Gastrointestinal, vs. tissue dwelling, vs. both!

Answer 198

Key events causing response: Parasite damage * Tuft cells in intestine * Epithelial cell response * Parasite antigen stimulation on APCs Impact of type-2 cytokine: Stimulates mast cell degranulation (increase gut motility, fluid secretion) Increase number of goblet cells –mucus hypersecretion (trap parasites). Release of toxic proteins, directly harm parasites. Increased epithelial cell turnover and intestine peristalsis. All lead to parasite expulsion Type 2 causes collagen synthesis and fibrosis due to arginase converting argine

Answer 199

Caused by macrophages

Answer 200

yes - they can suppress the immune system in useful ways

Answer 201

Type 1 immunity for protoza Type 2 immunity for Metazoan Balanced immunity is essential to avoid host damage

Answer 202

Low levels of resistance to vaccines are a consequence of the timing of the treatment (prevent rather than treat infection) and the multiplicity of target sites

Answer 203

Live vaccines Living, but cannot cause disease Killed vaccines Killed by heating, or exposure to chemicals Sub-unit vaccines Fragments of the microorganism e.g. proteins (or polysaccharides) Almost always antibody mediated In some cases an immune response against a single protein antigen elicits protection Nucleic acid vaccines (DNA or mRNA) Direct protein expression after injection Vectored vaccines DNA encoding the sub-unit is cloned into another “safe” microorganism

Answer 204

Removes toxicity of a protein The immunogenicity of the protein is preserved Problems: Must balance cross linking with retention of antigenic structure Batch to batch variation Reversion Requires pure toxin at the starting point: Needed to grow pathogen Need to purify and handle the toxin

Answer 205

Modern approach to subunit vaccines against toxins Modify the gene so that it encodes a non toxic (but immunogenic) protein

Answer 206

causes enterotoxaemia in livestock Produced in intestine crosses gut wall, targets kidneys and brain causing death Can mutate the toxin now 1000 fold less toxic Is a vaccine

Answer 207

Mutation in the catalytic A-subunit blocks activity Glycine to glutamic acid substitution at residue 52

Answer 208

Produce in harmless bacterium High yields Molecular structure more similar to active toxin Reproducible properties No reversion

Answer 209

F1 antigen - capsule and V-antigen part of the type 111 system are the protective components Then produce F1 and V antigens using genetic engineering Together produces solid protection

Answer 210

The spike S1 protein induces protective immune responses Some antibodies against S1 protein epitopes are protective others make the disease worse

Answer 211

Predict vaccines from the genome sequence Neisseria meningitidis causes globally 1.2 million invasive disease cases and 135,000 deaths per year • Serogroup B strains are the main cause of disease in Europe, New Zealand, Australia, Argentina, Canada, Japan • Traditional vaccinology had failed to identify a vaccine pSORT predicts cellular location so can help us find proteins that will be on the surface will give lots of proteins then you have to test them

Answer 212

H binding protein (fHbp), fused with NA2091 protein, binds human factor H, a negative regulator of the alternative pathway of complement activation. NadA, major adhesion protein involved in colonization, invasion, and induction of pro-inflammatory cytokines. NHBA, heparin-binding protein that increases resistance against the bactericidal activity of human serum PorA 1.4 Porin, A major outer membrane protein and the target for bactericidal antibodies

Answer 213

Agglutination Opsonization Neutralization Activation of complement Inflammation Antibody - dependent cell mediated cytotoxicity

Answer 214

No they are unique

Answer 215

Streptococcus pneumoniae - pneumonia • Haemophilus influenzae - pneumonia • Neisseria meningitidis - meningitis • Salmonella typhi – typhoid fever

Answer 216

Major cause worldwide of community acquired pneumonia, bacterial meningitis, bacteraemia and otitis media Causes disease in young and elderly Antibody against the capsular polysaccharide is protective Antibody causes: Opsonising Agglutinating Complement fixing

Answer 217

Polysaccharide diversity so doesn't work on slightly different strains * At risk populations respond poorly to vaccines * Poor long-term memory

Answer 218

Pick the serotypes most likely to cause disease and isolate these polysaccharides Created a 23-valent vaccine

Answer 219

Yes No involvement of antigen presenting cells, CD4+ or CD8+ T cells • Polysaccharides interact directly with B-cells • Clonal proliferation of B-cells • Production of IgM antibody • Poor antibody responses in children & in the elderly • no memory Can fix this by chemically coupling it to a protein which means it can now be processed

Answer 220

Glycoconjugate is internalized into an endosome of an antigen presenting cell (e.g. B cell). • processedintoglycanP-peptides.The polysaccharide is broken down into ~10kDa glycans • MHCII presentation of glycanP-peptide by MHCII to the αβ receptor of CD4+ T cells (αβTCR). •The T-cells involved are called T cells carb •Activation of the T cell results cytokines which mature the B cell to become a memory B cell (especially IL2 and IL4)

Answer 221

diphtheria toxin CRM197 genetic toxoid • glycine to glutamic acid substitution at residue 52 abolishes toxicity

Answer 222

Diseases where the microbe grows within host cells tuberculosis • salmonellosis • melioidosis • viral infections yellow fever influenza Measles SARS CoV2

Answer 223

induced by live attenuated microbes that can invade host cells Usually very effective – excellent mimetics of the natural microbe Risk is that they will still cause disease in some individuals e.g. immunocompromised Activates Another approach: Injected DNA or mRNA is taken up by host cells The protective sub-unit is produced by host cells and seen as foreign by the immune system Protein antigen is processed via the MHC I (and MHC II) pathways. Combine the advantages of live and sub-unit vaccines Work well in animals not really humans

Answer 224

Inset gene encoding the protective subunit into a “harmless” microbe • A wide range of carrier microbes have been suggested e.g. – Disabled Salmonella – Lactococcus – Vaccinia virus

Answer 225

Because most antigens carry many different epitopes, animals injected with a single antigen will produce a complex mixture of antibodies, each made by a different clone of B cells This antibody response is said to be polyclonal and will not discriminate between different antigens To discriminate between different antigens, antibodies need to be identified that bind to epitopes specific to individual antigens These are known as monoclonal antibodies

Answer 226

Allows the identification and culture of cells secreting identical antibodies with pre-defined specificity A single clone of cells secreting a single antibody is made by fusing a B cell (Ig+ splenocyte with finite lifespan) with a myeloma cell (cancerous Ig- B cell with infinite lifespan) The resulting hydrid cells (HYBRIDOMAS) each make a specific monoclonal antibody

Answer 227

Primary injection: Production of IgM Multivalent Low affinity Secondary injection: Production of IgG Bivalent Low to medium affinity Tertiary injection: Production of IgG Bivalent Medium to high affinity Multiple boosts: IgG Bivalent High affinity

Answer 228

HGPRT = Hypoxanthine:guanine phosphoribosyl transferase = blocks RNA and DNA transcription only can go through salvage pathway Spleen cell = HGPRT+ but is not able to grow in long-term Myeloma cell =HGPRT-, therefore not able to use the salvage pathway for RNA synthesis because the normal pathways are blocked Hybridoma cell = has HGPRT from a spleen cell and immortality from a myeloma cell, therefore is able to grow in the HAT medium (providing there is an exogenous supply of Hypoxanthine and Thymidine)

Answer 229

Plate-Trapped-Antigen-Enzyme-Linked Immunosorbent Assay Find out antibody is present when substrate added for target antigen goes from purple to yellow

Answer 230

An issue with hybridoma technology is immuno- dominance Alternative technologies to generate mAbs include phage display A technique in which antibody fragments are expressed as a fusion with a coat protein of a bacteriophage Fused proteins are displayed on the surface of the virion, while the DNA encoding the fusion resides within the virion

Answer 231

B cell source (from immunised animal) extract the mRNA reverse transcribe to get cDNA PCR to amplify each of the V-gene families Assesmble the VH and VL genes ar random (creates novel antibody repertoire with new pairings and specificities not present in donor) Clone as scFv or F(ab) onto pIII or pVIII

Answer 232

scFv = VL and VH (V heavy and V light) domains of an immunoglobulin linked by a peptide spacer Fusion proteins between scFv and pIII minor coat protein allows expression of scFv on surface of phage Five copies of PIII expressed Up to five scFv can be expressed on phage

Answer 233

F(ab) fragments of antibodies can be expressed on the surface of phage as fusion proteins with pIII Multiple copies expressed along the length of the phage particle

Answer 234

Diagnostic pathology (cytology and histology) In vitro diagnostic assays based on e.g. Enzyme-Linked Immunosorbent Assay (ELISA), Lateral-Flow Assay (LFA) for pathogens and biomarkers of disease (Lectures 15 & 16) Affinity purification and characterisation of antigens Limited use of mouse mAbs in vivo until relatively recently

Answer 235

Immunogenicity - most mAbs used in vivo are of mouse origin and are therefore XENOGENEIC resulting in Human Anti-Mouse Antibody (HAMA) reactions 2. Origin - Mouse origin diminishes their ability to elicit effector mechanisms such as COMPLEMENT-MEDIATED LYSIS or ANTIBODY-DEPENDENT CELL-MEDIATED CYTOTOXICITY (ADCC)

Answer 236

Use of xenoantibodies in human patients had proved to be severely limiting owing to their being seen as foreign proteins by the patient’s immune system Strategies adopted to increase the human content of antibodies which have proven clinical applications include: Production of human hybridomas from human B lymphocytes Replacement of the constant regions of mouse mAbs with those of human antibodies yielding CHIMERIC antibodies Replacement of complementarity-determining regions (CDRs) of a human antibody with those of a mouse antibody via CDR GRAFTING to make a HUMANISED antibody Production of FULLY HUMAN mAbs in transgenic mice

Answer 237

CRISPR-Cas9 technology used to knockout Prkdc and IL2rg loci Prkdc and IL2rg are part of the SCID (Severe Combined Immuno Deficiency) family of genes affecting maturation and formation of T cells, B cells, NK cells and other leukocytes Knockout renders mice immunodeficient Transplantation and engraftment of human HSC leads to mice with HIS

Answer 238

Immunocompromised individuals more susceptible to cancer than general population Some cytokines e.g. IL-2 are immuno-protective against cancer (IL-2 treatment is FDA approved for some cancers) The tumour micro-environment is rich in Tumour Infiltrating T-lymphocytes (TILs)

Answer 239

Elimination: By B cells, antibody, T cells, Treg cells, NK caells This is the innate and adaptive immune response active against tumour Can result in tumour cells death Equilibrium: Tumour is contained by the immune system but not completely destroyed Escape: Tumour antigen editing via genomic instability causes immune evasion Tumour microenvironment becomes immunosuppressive

Answer 240

Immunocompromised individuals more susceptible to cancer than general population Some cytokines e.g. IL-2 are immuno-protective against cancer (IL-2 treatment is FDA approved for some cancers) The tumour micro-environment is rich in immune suppressive signals such as: + High levels of suppressive cytokines + Infiltration of Tregs (inhibit dendritic cells and therefore T cell activation) + Low MHC expression on tumour cells + High expression of immune checkpoint proteins on T cells + High expression of immune checkpoint protein inhibitors on tumour cells

Answer 241

Specific: Trains the immune system to recognise and target only cancer cells Powerful: Attacks the cancer systemically through out the body Universal: A treatment approach that can be applied to nearly all cancers Memory: Capacity for memory means durability of protection

Answer 242

Passive vaccination (Therapeutic Monoclonal Antibodies) Active vaccination e.g. HPV vaccine (Gardasil, Cervarix) and cervical cancer Immune system modulators e.g. IL-2 (activates CD8 T cells) Immune Checkpoint Modulation Immune Cell Therapy

Answer 243

Carry cytotoxic agents to tumour Induce Complement-Mediated Lysis or ADCC of tumour cells e.g. Rituximab Block activity of tumour-specific proteins e.g. Herceptin Steps: Naked MAb Immunoconjugates Multistep targeting

Answer 244

Non-Hodgkin’s Lymphoma (NHL) is a malignant growth of B cells that results in tumors in lymph nodes and throughout the body No cure for most patients, and only 60% of patients treated with radiation and chemotherapy are still alive after 5 years

Answer 245

Rituximab is the first monoclonal antibody treatment approved for cancer Rituxan is a chimeric human-mouse mAb targeted against CD20, an antigen present on the surface of neoplastic B cells It consists of a human IgG1k antibody, with mouse variable regions isolated from a murine anti-CD20 mAb, IDEC-2B8 In vitro studies show the mAb is able to lyse CD20+ cells using human complement or ADCC

Answer 246

Breast cancer is a common cancer and 1 in 9 women will develop it during their lifetime. It also occurs in men. The reasons for breast cancer are not well understood. Only 5-10% of cases are thought to be inherited Two breast cancer genes have been identified: BRCA1 and BRCA2 The most frequent mutations in BRCA1 - common in a single group, the Ashkenazi Jews Women with mutations in the BRCA2 tumor suppressor gene have a greatly elevated risk of developing breast and ovarian cancers Breast cancer cells express an antigen (protein) on their surface called HER2 Breast cancer cells divide and grow when the protein Human Epidermal Growth Factor attaches itself to HER2

Answer 247

Herceptin is a humanised monoclonal antibody It blocks attachment of human epidermal growth factor to HER2 Herceptin is mainly used to treat women with advanced breast cancer and is given in combination with chemotherapy drugs such as Taxol After surgery, Herceptin treatment in combination with chemotherapy halved the rate of recurrence

Answer 248

Solanezumab (Sola) neuroprotector mAb binds to amyloid-b peptides Binds to central epitope KLVFFAD with picomolar affinity Epitope is nucleation site for Ab polymerization Oligomers of Ab toxic to neurons

Answer 249

Tocilizumab Humanised anti - human IL - 6R receptor antibody Blocks binding of IL - 6

Answer 250

Co-stimulation via CD28 ligation transducer T cell activating signals CTLA-4 ligation on activated T cells down regulates T cell responses Blocking CTLA-4 ligation enhances T cell responses Immune Checkpoint Proteins (e.g. CTLA-4) keep immune responses in check by preventing overly intense responses that might damage normal cells Blocking the activity of immune checkpoint proteins releases the "brakes" on the immune system, increasing its ability to destroy cancer cells The first such drug to receive FDA approval, ipilimumab (Yervoy®), for the treatment of advanced melanoma, blocks the activity of a checkpoint protein CTLA-4 which is expressed on the surface of activated Cytotoxic T-Cell. This increases T-Cell activation.

Answer 251

approved for patients with melanoma, lung cancer, renal cell carcinoma, Hodgkin lymphoma, head and neck cancer, colon cancer, liver cancer

Answer 252

approved for patients with melanoma, lung cancer, head and neck cancer, Hodgkin lymphoma and stomach cancer

Answer 253

Investigated immune modulatory drug for rheumatoid arthriris Binds to CD28 co-stimulator pair on T cells Potent agonist - stimulates anti inflammatory cytokine production However caused severe inflammatory reactions due to cytokine release syndrome

Answer 254

Idea behind this approach is that the TILs have already shown the ability to target tumor cells, but there may not be enough of them within the tumour to eradicate it or overcome the immune suppressive signals that are being released there Introducing massive amounts of activated TILs can help to overcome these barriers and shrink or destroy tumors In some experimental cases these treatment responses have lasted for years TILs are collected from samples of the tumor TILs that show the greatest recognition of the patient’s tumor in lab are selected Cells are then activated with cytokines and infused into the patient’s bloodstream

Answer 255

T cells are engineered to have a specific transgenic TCR which we know has high affinity to a certain tumour antigen

Answer 256

Another form of ACT that is being actively studied is Chimeric Antigen Receptor Modified T Cells (CAR-T cells) A patient’s isolated T cells are collected from the blood and genetically modified to express a protein known as CAR CARs are modified forms of a T cell receptor, which is expressed on the surface of T cells. These receptors allow the modified T cells to attach to specific proteins on the surface of cancer cells. Once bound to the cancer cells, the modified T cells become activated and attack the cancer cells The modified cells are grown in the laboratory to produce large populations of the cells CAR-T cells are then infused into the patient.

Answer 257

Sensitive signal amplification derived by evolution Low avidity Targets intracellular proteome Requires MHC class 1 expression and HLA matching on tumor cell Possible misfiring with endogenous TCR

Answer 258

Signal amplification derived by synthetic biology Avidity controllable Targets only surface structures HLA independent antigen recognition No misfiring with endogenous TCR

Answer 259

``` Radio-labeled antibodies used in nuclear medicine to locate cancer cells (or infections) by molecular imaging using: ``` Computed Tomography (CT) Magnetic Resonance Imaging (MRI) Positron Emission Tomography (PET) - PET/CT or PET/MRI Antibody Capromab reacts with prostate membrane specific antigen (PMSA) on prostate cells Can be conjugated to 111I with chelator pendetide and the radio-labeled antibody (trade name Prostascint) used to locate cancerous prostate cells. Others include antibody J591.

Answer 260

Monoclonal antibodies produced using hybridoma or phage display technologies are highly specific and can be used in immunotherapy and molecular imaging of cancers Tumour associated antigens can be recognized by the immune system Tumours adapt to evade immune clearance by mechanisms that either prevent recognition or that directly interfere with immune mediators There at least 5 different modalities to circumvent this immune evasion These modalities are collectively known as cancer immunotherapy The most promising tools are immune checkpoint inhibitors and CAR-T T cells

Answer 261

OID is a qualitative technique for detecting antibody-antigen interactions in which antigens and antibodies are placed in a gel of agar and allowed to diffuse towards one another A positive reaction is indicated by the presence of PRECIPITIN lines due to a Antibody-antigen equivalence = immune complex formation Antigen excess or antibody results in no precipitin

Answer 262

A cross sword

Answer 263

Arc on the side which doesn't have an extra shared one Spur forms on side that does, so cross bridge shape there

Answer 264

A technique in which specific antibodies are used to identify particular antigens in mixtures of proteins that have been resolved and transferred to a membrane The proteins are separated by an appropriate technique, usually SDS-PAGE (POLYACRYLAMIDE GEL ELECTROPHORESIS) Transfer is carried out by electroblotting to a sheet of nitrocellulose or PVDF, which is then incubated with labeled antibodies specific for the antigen of interest Radiolabeled or enzyme-linked antibodies can be used Unbound antibodies are washed away, and the position of the labeled antibodies is revealed using an appropriate technique ``` Chemical substrates (Chemiluminescent or Colourimetric) Radiography ```

Answer 265

The speed of migration in an electrical field depends on the dimension form and charge of molecules For deaggregation and denaturation of the proteins SDS, B-mercaptoephanol or DTT (reducing agents) and heat is used SDS provides negative charge to the proteins Right to left = separated by charge by isoelectric focusing (IEF) Up to down = separated by size by SDS electrophoresis

Answer 266

A qualitative technique in which antibodies tagged with fluorescent reagents (Fluorescein IsoThioCyanate or Texas Red) are used to detect molecules of interest. FITC and TR fluoresce under UV at different absorbance and emission spectra IF is one of the most widely used techniques in immunology, cell biology and clinical medicine Used to localise antibodies or antigens on cell surfaces or inside cells and to identify pathogenic organisms in tissues or exudates IF can be DIRECT or INDIRECT

Answer 267

Treatment on cell with labelled antibody Unbound antibody washed away and UV light applied Fluorescence observed where antigen is located

Answer 268

Treatment with unlabelled primary antibody Unbound antibody washed away Treatment with labelled secondary conjugate Unbound conjugate antibody washed away UV light applied Fluourescnce observed where antigen is located

Answer 269

A qualitative technique in which antibodies tagged with gold particles are used to detect molecules of interest EM-gold allows localisation of antigen-antibody interactions at the nm scale (cf. IF at the m) A powerful method of visualising intracellular antigens and organelles

Answer 270

ELISA is a quantitative technique for detecting antigens or antibodies using enzyme-substrate reactions The enzymes are usually coupled to antibodies either DIRECTLY (to the antibody specific for the antigen) or to anti-immunoglobulins (INDIRECTLY) The two main ELISA formats are: 1. Plate-Trapped-Antigen (PTA)-ELISA 2. Sandwich-ELISA Quantification in ELISA is achieved using standard calibration curves

Answer 271

Direct Indirect Sandwich ELISA CompetitiveELISA

Answer 272

Ubiquitous soil-borne plant pathogen with worldwide distribution and wide host range Difficult to control using chemicals Soil dwelling Widespread resistance to fungicides Soil fumigants are banned (Class II ozone depletors) Most effective way to prevent disease is to ‘evade’ the pathogen altogether - test soils for infestation prior to sowing with susceptible crops R. Solon-specific mAbs = Monoclonal antibodies raised against a surface glycoprotein antigen mAb EH2 - protein epitope mAb EE1 - carbohydrate epitope Antigen is secreted by live cells only Proces: Stimulate active growth using baits 2. Detect R. solani using specific mAbs 3. Recover positive isolates for further testing

Answer 273

Coat plates with mAb EH2 16h at 4 degrees Bait incubation 2h and 23 degrees add mAb EE1, 1h at 23 degrees Anti-IgM (u-chain specific) peroxidase conjugate (1h at 23 degrees Substrate formed 30min at 23 degrees

Answer 274

amphibian killer Spores swim towards spogs Burrow into them Mature into sporangium Spores released Kills the frog within 120 days Kills by colonising keratinised skin layer Hyperplasia + Hyperkeratosis = disrupted electrolyte balance Leads to cardiac arrest and death

Answer 275

Caused by Aspergillus fumigatus Most important opportunistic mould pathogen of immuno-compromised humans esp. haematological malignancy and bone marrow transplant patients Can result in - Invasive Pulmonary Aspergillosis >300,000 cases/year worldwide with 30-95% mortality Chronic Pulmonary Aspergillosis ~3 million cases worldwide in patients with underlying lung diseases including asthma Allergic Bronchopulmonary Aspergillosis ~4 million cases worldwide in patients with asthma and cystic fibrosis Covid-19-Associated Pulmonary Aspergillosis (CAPA) / IAPA?

Answer 276

Diagnosis notoriously difficult - patient history, culture from invasive biopsy, and biomarkers in invasive BALf or in blood Hospital treatments ‘fever-driven’ or by non-specific chest CT - patients can receive inappropriate treatment with costly and toxic antifungal drugs Imperative that diagnosis is made without delay - prognosis worsens rapidly over time with high mortality - exacerbated by poor diagnosis Drug resistance in clinical strains of Aspergillus is increasing

Answer 277

IgG3 immunoglobulin Recognises extracellular glycoprotein antigen Antigen is secreted during active growth of hyphae and is not produced by dead or dormant spores JF5 used to develop a rapid, user-friendly, diagnostic test (lateral-flow assay) for detection of IPA using BALf and serum

Answer 278

Lung fluid

Answer 279

Institute to industry Patent to product Bench to Bedside

Answer 280

Can use it show up Aspergillus infection in a scan It acts as a tracer Depletion of neutrophil granulocytes in C57BL/6 mice via injection (i.p.) of the anti Gr-1 antibody RB6-8C5 Intratracheal (i.t.) infection of neutropenic C57BL/6 mice with A. fumigatus conidia In vivo & ex vivo bio-distributions of [64Cu]-labeled antibody tracers measured in lungs via how much radioactivity there is Next step of developing the technique - Humanisation of JF5 by CDR grafting Proved that the target epitope (b1,5-galactofuranose ) of the antigen is not present in humans