Immunology Flashcards
What is innate immunity?
Non-specific, instinctive, does not depend on lymphocytes.
What is adaptive immunity?
Specific ‘Acquired’ immunity, requires lymphocytes, antibodies.
What does humeral mean?
Made up of cells and soluble proteins.
What do neutrophils do?
Important role in innate immunity, phagocytosis.
What are the two main intracellular granules in a neutrophil?
Primary lysosomes - contain myeloperoxidase, muramidase, acid hydrolases, proteins (defensins)
-Secondary granules containing lactoferrin and lysozyme.
What do primary lysosomes do in neutrophils?
Primary lysosomes combine with phagosomes containing microbes to digest them.
Have Fc and complement receptors
Can kill microbes by secreting toxic substances (superoxides)
What do monocytes do?
Play important role in innate and adaptive Immunity ,
Phagocytosis & Ag presentation.
Remove anything foreign (microbes) or dead.
What do monocytes have on their surface?
Have Fc, complement receptors
also Pattern Recognition Receptors (PRR)
Toll-like and mannose receptors
Can bind to all kinds of microbes.
What do monocytes contain to kill microbes?
Peroxidase.
What do macrophages do?
Play important role in Innate and Adaptive Immunity –
Phagocytosis & Ag presentation.
Remove foreign (microbes) and self (dead/tumour cells) .
What do macrophages contain on their surface?
Have Fc, complement receptors
also Scavenger,
Toll-like and mannose receptors –
Can bind all kinds of microbes.
What is an Eosinophil associated with?
Mainly associated with parasitic infections and allergic reactions.
What do the granules in an eosinophil contain?
Major basic protein, potent toxin for helminth worms.
What does major basic protein do?
Activates neutrophils
Induces histamine release from mast cells & provokes bronchospasam.
What does a basophil do?
Very similar to mast cells
Express high-affinity IgE receptors (FcdeltaR1).
What does binding of IgE to receptor cause to basophils?
Binding of IgE to receptor causes de-granulation releasing histamine – main cause of allergic reactions.
Mainly involved in immunity to parasitic infections and allergic reactions.
What are mast cells? What do they do?
Only in tissues (precursor in blood)
Very similar to basophils
Express high-affinity IgE receptors
Mainly involved in immunity to parasitic infections and allergic reactions
What does binding of IgE to mast cells do?
Binding of IgE to receptor causes de-granulation releasing histamine – main cause of allergic reactions (Done in 3rd year)
What is the T cells main role in adaptive immunity?
Recognise peptide Ag displayed by Antigen Presenting Cells (APC)
What are the main types of T cells and what does each do?
T helper 1 (CD4 – ‘help’ immune response intracellular pathogens)
T helper 2 (CD4 – ‘help’ produce antibodies – extracellular pathogens)
Cytotoxic T cell (CD8 – can kill cells directly)
T reg (FoxP3) – regulate immune responses ‘dampen’
Where are T cells found?
Blood, lymph nodes and spleen.
What do B cells do?
Recognise Ag displayed by Antigen Presenting Cells (APC)
Express membrane bound antibody on cell surface.
Differentiate into plasma cells that make Antibodies.
Where are B cells found?
Blood, lymph nodes and spleen.
What do natural killer cells do and how do they do it?
Recognise and kill:
Virus infected cells.
Tumour cells.
By apoptosis.
Type of lymphocyte
What are the soluble factors of immunity?
Complement.
Antibodies.
Cytokines, Chemokines.
What is the complement system?
Group of ~20 serum proteins that need to be ‘activated’ to be functional.
What are the different ways the complement system can be activated?
Classical - Ab bound to microbe.
Alternative – C’ binds to microbe.
Lectin – activated by mannose binding lectin bound to microbe.
What does C3a do?
Recruits neutrophils to the site.
What does C5 do?
Recruit membrane attack pathway.
What is an immunoglobulin?
Soluble.
Bound to B cells as part of B-cell antigen receptor.
What are the classes of immunoglobulin?
IgG (IgG1-4).
IgA (IgA1 & 2).
IgM.
IgD.
IgE.
What is an antibody?
Protein produced in response to an antigen.
It can only bind with the antigen that induced its formation – i.e. specificity.
What is an antigen?
A molecule that reacts with preformed antibody and specific receptors on T and B cells.
What is an epitope?
The part of the antigen that binds to the antibody/receptor binding site.
What is affinity?
Measure of binding strength between an epitope and an antibody binding site. The higher the affinity the better.
What is the most common Ig in serum?
IgG.
What are the properties of IgM?
Accounts for 10% of Ig in serum Pentamer.
Mainly found in blood – big so not cross endothelium
The monomeric form (mIgM) is present as an antigen-specific receptor on B cells.
What Ig is produced first in primary response?
IgM
Which Ig is predominant in mucus?
The predominant Ig in mucous secretions such as saliva, colostrum, milk, bronchiolar & genitourinary secretions
Called Secretory IgA (sIgA)
What is IgA in the blood?
A monomer.
How does IgE react with basophils and mast cells to produce a response?
Basophils and Mast Cells express and IgE-specific receptor that has high affinity for IgE.
Basophils and Mast Cells are continually saturated with IgE.
Binding Ag triggers release of histamine by these cells.
What are cytokines?
Proteins secreted by immune and non-immune cells.
What are the different kinds of cytokines?
Interferons (IFN).
Interleukins (IL).
Colony Stimulating Factors (CSF).
Tumour Necrosis Factors (TNFalpha & beta).
What do interferons do?
Induce a state of antiviral resistance in uninfected cells & limit the spread of viral infection.
- IFNa & b - produced by virus infected cells
- IFNg - released by activated Th1 cells
What do interleukins do?
Produced by many cells, over 30 types
- Can be pro-inflammatory (IL1) or anti-inflammatory (IL-10)
- Can cause cells to divide, to differentiate and to secrete factors.
What do colony stimulating factors do?
Involved in directing the division and differentiation on bone marrow stem cells
– precursors of leukocytes.
What do tumour necrosis factors do?
Mediate inflammation and cytotoxic reactions.
What do chemokine do?
Group of approx 40 proteins that direct movement of leukocytes (and other cells) from the blood stream into the tissues or lymph organs by binding to specific receptors on cells.
They attract leukocytes to sites of infection/inflammation.
What protection does the innate immune system confer?
Physical and chemical barriers.
Phagocytic cells (neutrophils and macrophages).
Serum proteins (complement, acute phase).
What are the barriers to pathogens?
Skin.
Dermis & Epidermis
Sebum.
(skin secretions) pH 3-5.
Intact skin.
Prevents penetration
Prevents growth (low pH).
What mucous membranes do we have?
Saliva
Tears
Mucous secretions
Mucous - entrapment
Cillia – beating removes micrbes
Commensal colonies – attachment, nutrients.
What physiological barriers do we have?
Temperature (pyrexia).
Fever response inhibits micro-organism growth.
pH
Gastric acidity (Helicobacter pylori)
Neonate stomach less acidic than adult
and so susceptible to infection
Oxygen tension - aerobes/anaerobes
What happens in inflammation?
Stop bleeding (coagulation)
Acute inflammation (leukocyte recruitment)
Kill pathogens, neutralise toxins, limit pathogen spread
Clear pathogens/dead cells (phagocytosis)
Proliferation of cells to repair damage
Remove blood clot – remodel extracellular matrix
Re-establish normal structure/function of tissue
What are the properties of inflammation?
Increased blood supply
Increased vascular permeability
Increased leukocyte transendothelial migration ‘extravasation’.
What happens in acute inflammation?
Complete elimination of a pathogen followed by resolution of damage, disappearance of leukocytes and full regeneration of tissue.
What happens in chronic inflammation?
Persistent, un-resolved inflammation.
How does the complement system work?
Lyse microbes directly (Membrane Attack Complex).
Increase chemotaxs (C3a and C5a).
Opsonisation (C3b).
What is extravasation?
Movement of white blood cells from the capillaries to the tissues surrounding them (leukocyte extravasation), also known as diapedesis.
What is the method of phagocytosis?
Binding
Engulfment
Phagosome formation
lysosome formation
membrane disruption/fusion
What are the two mechanisms of killing In polymorphs and macrophages? What happens in each case?
Oxygen dependent and oxygen independent.
Oxygen dependent.
Reactive Oxygen Intermediates (ROI)
Superoxides (O2 ) converted to H2O2 then ·OH (free radical)
Nitric Oxide (NO) - vasodilation (Viagra) increases extravasation but also directly anti-microbial.
Oxygen independent.
Enzymes - defensins (insert into membranes), lysozyme pH, TNF
What are acute phase proteins? What are the acute phase proteins?
Present in blood and increase during infection.
C Reactive Protein
Serum protein produced by liver, binds to some bacterial cell walls (pneumococci). Promotes opsonisation, binds to C1q and activates C’
Mannose binding lectin (MBL)
Binds to lectin on microbes, promotes opsonisation (via MBLR) and activates C’
Surfactant protein-A (SP-A)
Binds haemagglutinin in influenza – reduces ability of virus to infect cells
Why do we need the adaptive immune system?
Microbes evade innate immunity (Dr Stafford) (proteases, decoy proteins, etc)
Intracellular viruses and bacteria ‘hide’ from innate immunity
What does cell-mediated immunity require?
Intimate cell to cell contact.
–control Ab responses via contact with B cells
–directly recognise and kill viral infected cells
Major Histocompatibility Complex (MHC)
Intrinsic/Endogenous (intracellular) antigens
Extrinsic/Exogenous (extracellular) antigens
Recognise ‘Self’ or ‘Non-Self’.
What is cell-mediated immunity a contact with?
Antigen presenting cells and T cells.
What do T cells respond to?
Only respond to presented antigens NOT soluble ones.
What is T cell selection?
T cells that recognise self are killed in the thymus during pregnancy.
What does a T cell need to recognise a foreign antigen?
A major histocompatibility complex.
What do major histocompatibility complexes do?
Display peptides from self OR non-self proteins (eg. degraded microbial proteins) on the cell surface – invasion alert.
What are major histocompatibility complexes coded by?
Human Leukocyte Antigen (HLA).
Where are MHC class 1 located?
All cells. glycoproteins
Where are MHC class 2 located?
on APCs. Glycoproteins.
Where are MHC class 3 located?
Secreted proteins.
How is an intrinsic antigen dealt with?
Class I All cells
Tc (CD8)
Kill infected cell with intracellular pathogen.
How is an extrinsic antigen dealt with?
Class II APC only.
Th (CD4).
Help B cells make Ab to extracellular pathogen, can help directly kill.
What happens at T cell activation? What does this lead to?
IL-2 is secreted & binds to IL-2R on T cells (autocrine).
Division, differentiation, effector functions, memory.
What does a CD8 cell do when it’s activated?
CD8 + MHCI/peptide = Tc / CTL (effector cell)
CTL forms proteolytic granules & releases perforins and granulysin
Also induces apoptosis (cell suicide).
How does CD4 T cell activation work?
APC presents Ag with MHC II to naïve CD4 T cell
Stimulation with high levels of IL-12 activate naïve cells to Th1 cells
Th1 cells go to secondary lymphoid tissue (spleen, lymph nodes)
Activated Th1 (CD4) cells proliferate (clonal expansion)
Th1 cell recognises Ag on infected cells (with MHC II) via TCR (CD4)
Th1 secretes INFγ – stop virus spread (and apoptosis).
How do B cells present an antigen to T cells?
Monomeric IgM (or mIgD) binds Ag
Phagocytosis
Peptide displayed on surface with MHC II
TCR of naive Th (CD4) binds to MHC II
Lots of other co- stimulatory molecules required.
How does clonal expansion of B cells happen from T cell activation?
APC eats Ag (extrinsic) and presents it to naïve CD4+ T cells (via MHC II)
These turn into Th2 cells
Th2 cells bind to B cells that are presenting Ag (via MHC II). This Ag has been captured using the mIgR on cell surface.
Th2 cell now secretes cytokines (IL-4, IL-5, IL-10 and IL-13 ( )
These cause B cells to divide – CLONAL EXPANSION and differentiate into
Plasma cells (AFC = antibody forming cell) and Memory B cells (Bm)
What happens in B cell activation?
Upon binding an Ag that ‘fits’ B cells become activated
Activated B cells go to the lymph nodes where they proliferate (clonal expansion) and differentiate into plasma cells
These plasma cells secrete Ab of same specificity but are generally IgM – these later turn into IgG but still have same specificity to the same Ag (class switching)
Some still express cell surface mIgM and recalculate for months (Memory B cells)
Re-stimulation of Memory B cells leads to secondary response - This is very quick
What do antibodies do?
Neutralise toxin by binding to it.
Increase opsonisation – phagocytosis.
Activate complement.
What are two regions on an antibody and why are they important?
RECOGNITION
Fab regions – variable in sequence Bind different antigens specifically.
ELIMINATION
Fc region – constant in sequence Binds to complement, Fc receptors on phagocytes, NK cells etc.
What is the basic structure of an antibody?
VARIABLE (V) regions - bind antigen. Differ between antibodies with different specificities.
CONSTANT (C) regions - same for antibodies of a given H chain class or L chain type.
VARIABLE and CONSTANT regions are encoded by separate exons.
Multiple V region exons in the genome can RECOMBINE and MUTATE during B cell differentiation to give different antibody specificities.
What are the different immunoglobulins?
IgG. IgM. IgA. IgD. IgE.
What are the two light chains of an antibody?
Kappa and Lambda.
What antibody responds first to an antigen?
IgM.
What antibodies can the secondary response involve?
IgA and IgE.
How can antibodies protect against infection? What does each of these involve?
SPECIFIC BINDING / MULTIVALENCY (Fab).
Neutralize e.g. toxins (IgG, IgA)
Immobilise motile microbes (IgM)
Prevent binding to, and infection of, host cells
Form complexes
ENHANCE INNATE MECHANSIMS (Fc).
Activate complement (IgG, IgM)
Bind Fc receptors
-phagocytes (IgG, IgA) – enhances phaogcytosis
-mast cells (IgE) – release of inflammatory mediators
-NK cells (IgG) – enhanced killing of infected cells
What does T cell-mediated immunity involve?
Mature in the thymus.
Bind antigen through specific T cell receptors.
Produce cytokines (augment/control behaviour of leukocytes).
Specifically kill infected host cells.
What do T helper cells do? CD4
Help B cells make antibody
Activate macrophages and natural killer cells
Help development of cytotoxic T cells.
What do T cytotoxic cells do? CD8
Recognise and kill infected host cells.
What do T regulatory cells do? CD4
Suppress immune responses.
How do MHC 1 and a T cytotoxic cell destroy an infected cell?
Cytotoxic T cell recognises peptide bound to MHCI.
Virus-infected cell → viral proteins, broken down in cytosol
Peptides transported to ER, bind MHCI → cell surface
Activated cytotoxic T cells kill the infected cell by inducing apoptosis.
How do MHC 2 and a T helper cell destroy an infected cell?
Macrophage/dendritic cell/B cell internalises and breaks down foreign material.
Peptides bind to MHC II in endosomes cell surface.
Activated T helper cells help B cells make antibody, produce cytokine that activate/regulate other leucocytes.
What are cytokines?
Small secreted proteins involved in communication between cells of the immune response.
- usually produced & act locally
- act by binding to specific receptors on the surface of target cells (cytokine receptors).
What are the main groups of cytokines?
Interleukins (IL-1, IL-38?) – usually made by T cells.
Interferons (IFNs) - viral infections e.g. IFN, IFN; cell activation (IFN ).
Chemokines - cell movement or chemotaxis e.g. IL-8.
Colony stimulating factors (CSFs) – leukocyte production e.g. M-CSF.
What do the different types of CD4 cells produce?
TH1 cells Produce IL-2, -interferon and TNF.
TH2 cells Produce IL-4,-5, -6, -10 and -13. \
TREG cells Produce IL-10, TGF β – down-regulate other T cell subsets.
What do TH1 cells do?
Activate macrophages inflammation.
Promotes production of
Cytotoxic T cells (classic CELL-MEDIATED immunity).
Important in intracellular infections.
Induce B cells to make IgG antibodies.
What do TH2 cells do?
Activate eosinophils and mast cells.
Important in helminth infections and ALLERGY.
Induce B cells to make IgE - promotes release of inflammatory mediators e.g. histamine from mast cells.
What is the hygiene hypothesis?
Insufficient exposure to certain types of infection (“dirt”) skews TH1/TH2 balance towards TH2?
BUT negative correlation between helminth infections and allergic disease.
What is the counter regulation hypothesis?
Infection protects against allergy by promoting IL-10 and TGFβ production (TREG ↑, TH1 and TH2↓).
What does a haemopoietic stem cells divide into?
lymphoid progenitor (B cell or T cells) or myeloid progenitor (macrophages, basophils).
What are the different types of PRRs?
Secreted and circulating PRRs
Cell-associated PRRs (more traditional receptors).
What are the secreted and circulating PRRs?
Antimicrobial peptides secreted in lining fluids, from epithelia, and phagocytes.
Defensins, cathelicidin
Lectins and collectins.
Mannose binding lectin (deficiency syndromes), surfactant proteins A and D.
What are lectins and collectins?
Lectins and collectins: carbohydrate-containing proteins that bind carbohydrates or lipids in microbe walls.
Activate complement, improve phagocytosis.
What are cathelicidins?
Cathelicidin-related antimicrobial peptides are a family of polypeptides found in lysosomes of macrophages and polymorphonuclear leukocytes, and Keratinocytes.
What are defensins?
Defensins are small cysteine-rich cationic proteins found in both vertebrates and invertebrates.
They have also been reported in plants.
They are, and function as, host defense peptides.
They are active against bacteria, fungi and many enveloped and nonenveloped viruses.
What are Pentraxins?
Proteins like CRP, which have some antimicrobial actions, can react with the C protein of pneumococci, activate complement, and promote phagocytosis.
What are cell-associated PRRs?
Receptors that are present on the cell membrane or in the cytosol of the cells.
Recognise a broad range of molecular patterns.
TLRs are the main family.
What are some other PRRs?
Mannose receptor on macrophages (fungi).
Dectin-1. Widespread on phagocytes, helps recognise beta glucans in fungal walls.
Scavenger receptors on macrophages.
What are NLRs?
Named after first members of the family, NODs, Nod-like receptors.
What does NOD2 do?
Widespread expression
Recognises muramyl dipeptide (MDP), a breakdown product of peptidoglycan
Activates inflammatory signalling pathways
Non-functioning mutations: Crohn’s disease
Hyperfunctioning mutations: Blau syndrome (rare, chronic granulomatous inflammation of skin, eyes and joints)
What do RLRs do?
Best known are RIG-I and MDA5, who’s roles are to detect intracellular double-stranded viral RNA and DNA.
They couple effectively to activation of interferon production, enabling an antiviral response
NOD2 can also activate anti-viral signalling
How are PRRs important in homeostasis?
Blood neutrophil numbers may be dependent upon TLR4 signalling, independent of LPS in homeostasis.
Induction of endotoxin tolerance in the newborn gut.
Maturation of the normal immune system.
Maintaining a balance with commensal organisms.
How are PRRs important with damage recognition?
TLRs also adapted to recognise a range of endogenous damage molecules, which may share characteristics of hydrophobicity.
Appearance of host molecules in unfamiliar contexts can activate TLRs.
TLR signalling by cellular damage products activates immunity to initiate tissue repair and perhaps enhance local antimicrobial signalling.
How do PRRs help in adaptive immunity?
Activation of TLRs and other PRRs drives cytokine production by antigen-presenting cells that can increase the likelihood of successful T cell activation.
TLR4 agonists already used as vaccine adjuvants.
TLR7/8/9 adjuvants in development.
How do PRRs help in disease?
Recognition of host molecules in autoimmune disease
Failure to recognise pathogens or increased inflammatory responses
Atherosclerosis, arthritis, COPD, etc.
What is passive immunity?
The administration of pre-formed immunity from one person or animal, to another person.
What is natural passive immunity?
The transfer of maternal antibodies across the placenta to the developing foetus/breast milk
Provides protection against:
Diphtheria
Tetanus
Rubella
Mumps
Poliovirus
What is artifical passive immunity?
Treatment with pooled normal human IgG or immunoserum against pathogens or toxins
- Individuals with inborn or acquired agammaglobulinaemias (B cell defects)
- Exposure to a disease that could cause complications (e.g. Immune-compromised patient exposed to measles or other pathogens)
- When there is no time for active immunisation to give protection
(e. g. a pathogen with a short incubation time) - Acute danger of infection
- Anti-toxins and anti-venins
(possibility of reactions)
What are the limitation of passive immunity?
Antibody mediated.
What are the advantages of passive immunity?
Gives immediate protection.
Effective in immunocompromised patients.
What are the disadvantages of passive immunity?
Short-lived. Possible transfer of pathogens. “serum sickness” on transfer of animal sera.
What are some specific passive immunisations?
Human tetanus immunoglobulin.
Human rabies specific Ig.
Human Hep B Ig.
Varicella Zoster Ig.
What is normal immunoglobulin?
Prepared from pools of at least 1000 donors, contains antibody against measles, mumps, varicella, hepatitis A etc.
What is the purpose of a vaccine?
- Manipulating the immune system to generate a persistent protective response against pathogens by safely mimicking natural infection (ideally from a small number of inoculations, IgG or IgA)
- Mobilise the appropriate arms of the immune system and generate immunological memory (B and/or T cell memory!)
- The importance of the memory B cell response depends on the nature of the pathogen!
PRODUCE PRIMARY RESPONSE WITH NO SYMPTOMS
What are the choices for a vaccine?
A. Whole Organism
Live attenuated pathogen
Killed, inactivated pathogen
B. Subunit
Toxoids
Antigenic Extracts
Recombinant proteins
C. Peptides
D. DNA Vaccines
E. Engineered Virus
What are live attenuated vaccines?
The organisms replicate within the host, and induce an immune response which is protective against the wild-type organism.
What are examples of live attenuated vaccines bacterial?
BCG.
Polio Sabin
What are the advantages of live attenuated vaccines?
Attenuated pathogen sets up a transient infection
Activation of full natural immune response
Prolonged contact with the immune system
Memory response in the T and B cell compartments
Resulting in prolonged and comprehensive protection
Often only a single immunisation is required – advantages in the Third World
What are some problems and limitations with live attenuated vaccines.
Immunocompromised patients (or other rare individuals) may become infected as a result of immunisation
Complications !
For example – live measles vaccine 1 per 1,000,000 - post-infectious encephalomyelitis
(0.5 – 1.0 per 1000 with natural disease)
Occasionally the attenuated organism can revert to a virulent form e.g. Polio Sabin (1 case in 2,400,000 doses)
In areas with poor sanitation this can lead to a serious outbreak – so Polio Salk is the preferred vaccine in the Third World
What are the advantages of whole inactivated pathogen?
No risk of infection
Storage less critical
A wide range of different antigenic components are present so a good immune response is possible
What are the problems and limitations with whole inactivated vaccines?
Tend to just activate humoral responses (lack of T cell involvement)
Without transient infection the immune response can be quite weak
Repeated booster vaccinations required
Patient compliance can be an issue
What are the problems and limitations with whole inactivated vaccines?
Tend to just activate humoral responses (lack of T cell involvement)
Without transient infection the immune response can be quite weak
Repeated booster vaccinations required
Patient compliance can be an issue
How are live pathogens inactivated?
Inactivation usually by chemical treatment
e.g. formaldehyde (Salk Polio vaccine/Hep A) –
heat inactivation can alter the conformation of the target antigens!
Why are some pathogens unable to produce vaccines from?
Pathogen too hard to grow.
Killed pathogen not protective.
Impossible to obtain attenuated and suitably immunogenic strain.
What are the subunit vaccines?
Purified molecular components as immunogenic agents
3 major types:
- Inactivated exotoxins (toxoids)
- Capsular polysaccharides (Men C)
- Recombinant microbial antigens (Bexsero)
What are the advantages of subunit vaccines?
Safe – only parts of the pathogen are used
No risk of infection
Easier to store and preserve
What are the disadvantages of subunit vaccines?
Immune response less powerful
Repeated vaccinations and adjuvants
Consider genetic heterogeneity of the population by the choice of antigen (HLA/cytokine expression)
What are synthetic peptides as vaccines?
Despite initial promise – the field has advanced slowly
Aim – to produce a peptide that includes immunodominant B cell epitopes and can stimulate memory T cell development
What is the difficulty with synthetic peptides as vaccines?
- It is now clear that knowledge of HLA presentation of peptides is essential
- Peptides can be stimulatory OR suppressive !
- Most B cell epitopes are conformational
What are DNA vaccines?
Aim – to transiently express genes from pathogens in host cells. Generates immune response similar to natural infection
Leading to T and B cell memory responses
What are the advantages of DNA vaccines?
Safe (especially in immunocompromised patients)
No requirement for complex storage and transportation
Drug delivery can be simple and adaptable to widespread vaccination programs (‘DNA gun’)
What are the disadvantages of DNA vaccines?
DNA vaccines are likely to produce a mild response and require subsequent boosting
No transient infection
What are recombinant vector vaccines?
Aim – to imitate the effects of transient infection with pathogen but using a non-pathogenic organism
Genes for major pathogen antigens are introduced into a non-pathogenic or attenuated microorganism and introduced into the host
What are some recombinant vector examples?
Viral or Bacterial
Vaccinia virus
Canarypox
Attenuated poliovirus
Attenuated strains of Salmonella
BCG strain of Mycobacterium bovis
What are the advantages of recombinant viral vaccines?
Create ideal stimulus to immune system
Produce immunological memory
Flexible - different components can be engineered in
Safe - relative to live attenuated pathogen
What are the disadvantages of recombinant Viral Vaccines?
Require refrigeration for transport
Can cause illness in compromised individuals
Immune response to virus in subjects can negate effectiveness
What are adjuvants?
Essentially any substance added to vaccine to stimulate the immune system
Can include:
- Whole killed organisms e.g. Complete Freud’s adjuvant (CFA), Mycobacterium tuberculosis – not used in human medicine!
- Aluminium salts
- Oil-in-water emulsions (MF59)
- Saponins (QS21)
- Monophosphoryl lipid A (MPLA)
- TLR agonists
What is a heterologous Prime-Boost?
Prime there response with a DNA vaccine.
Boost with a vectored vaccine or recombinant protein.
What is an allergy?
Abnormal response to harmless foreign material.
What is atopy?
Tendency to develop allergies.
What Ig’s are involved with allergies?
Mainly IgE, also IgG4 and IGA.
What indicates a strong indication of genetic factors in allergies?
Concordance in twin studies.
What cells are involved with allergies?
Mast, eosinophils, lymphocytes, dendritic.
Smooth muscle, fibroblasts and epithelia.
What are the mediators of allergies?
Cytokines, chemokines, lipids, small molecules.
How does IgE signal?
Receptors on the surface of mast cells cluster together and it’s this clustering and receptor cross linking which causes amplification and cellular responses.
Where is the low affinity IgE receptor FckappaRII found? What is its function?
B cells, T cells, monocytes, eosinophils, platelets and neutrophils.
Regulation of IgE synthesis.
Triggering of cytokine release by monocytes.
Antigen presentation by cells.
What cells express the high affinity IgE receptors and what is their role?
Eosinophils, Mast cells and Basophils.
Role in host defence against parasites.
What do mast cells do?
IgE-mediated immunity.
Main effector cells.
Primary role in innate and acquired immunity.
What do mast cells require to develop?
c-kit protein.
What preformed compounds do mast cells contain?
Histamine.
Chemotatic factors.
PROTEASES.
Tryptase.
Chymase.
PROTEOGLYCANS.
Chondrotin sulphate.
Heparin.
What lipid derived mediators do mast cells contain?
Leukotrienes.
Prostaglandin D2.
Platelet Activating Factor (PAF).
What do mast cell chemotactic factors typically lead to?
Eosinophil attraction and activation.
What does histamine cause?
Arteriolar dilation, capillary leakage.
Induces cholinergic reflex bronchoconstriction (bronchospasm).
What do Leukotrienes do?
Capillary endothelial contraction with vascular leakage: increased permeability.
What does prostaglandin do?
Potent inducer of smooth muscle contraction.
What does platelet activating factor do?
Increases platelet aggregation, degranulation; increases vascular permeability; activates neutrophil secretion.
What transcription/translation compounds do mast cells contain?
Cytokines.
What do mast cell derived cytokines do?
Promote a Th2 response and can lead to B cell class switching - IgE production.
What indirect activators of mast cells? Via IgE.
Allergens.
Bacterial/viral antigens.
Phagocytosis
What are direct activators of mast cells?
Cold/mechanical deformation.
Aspirin, tartazine, preservatives, NO2, latex, proteases.
Complement products (C3a, C5a)
What causes activation of mast cells?
Indirect activators.
Direct activators.
Phagocytosis of enterobacteria.
What is mast cell and IgE resistance to parasitic infections characterised by?
Th2 cytokines.
IL-3, IL4, IL-5, IL-10.
Recruit eosinophils, basophils and macrophages.
What is atopy?
A hereditary predisposition to the development of immediate hypersensitivity reactions against common environmental antigens.
What are some cells involved in allergies?
Lymphocytes.
Typically Th2.
Dendritic cells
-Antigen presentation.
Neurons.
-coughing, sneezing.
Other non-immune cells
-FIbroblasts, epithelia, Smooth muscle.
What makes an allergen?
Particulate delivery of antigens.
Presence of weak pathogen-associated molecular patterns (PAMP).
Nasal/skin delivery.
Low doses.
What are some allergic diseases?
Anaphylaxis.
Allergic asthma.
Allergic rhinitis.
Contact dermatitis.
Insect venom.
GI: food allergies.
How can the complement direct the immune response?
A foreign substance that has few PAMPS but causes complement activation is opsonised and activates macrophages through C5a: adaptive immunity is not switched on.
HOWEVER
A foreign substance that has few PAMPS AND does not activate complement: the antigen persists and adaptive immunity is switched on.
What happens at the cellular level with anaphylaxis?
Mast cell or basophil activation.
- IgE or direct activation.
- Serum tryptase, histamine elevated.
What happens with the bodies systems in anaphylaxis?
CV
-Vasodilation, increased vascular permeability, lowered BP.
Respiratory.
-Bronchial SM contraction, mucus.
Skin.
-Rash, swelling.
GI
-Pain, vomiting.
How can you treat an allergen?
Avoid allergens.
Desensitisation to allergen.
Prevent IgE production.
Prevent ice interaction with receptor.
Prevent mast cell activation.
Inhibit mast cell products.
What is desensitisation?
Increasing doses of antigen.
- Sub-lingual.
- sub-cutaneous.
How can you prevent IgE production?
Delivery of suppressive cytokines? IL-12 Reduces eosinophilia, Th2 responses in mice IL-18 Reduces IgE production in mice Blockade of cytokines? IL-4 antagonist (Pitakinra): Reduction in late-phase response Anti-CD23 antibodies can decrease IgE levels Lumiliximab Currently used for leukaemia
What is an example of a anti-IgE therapy?
Xolair (Omalizumab) is a recombinant DNA-derived humanized IgG1κ monoclonal antibody that selectively binds to human immunoglobulin E (IgE).
Xolair inhibits the binding of IgE to the high-affinity IgE receptor (FcεRI).
What are the disadvantages to anti-IgE therapy?
Very high cost
Slight increase in cancer incidence
Anaphylaxis
Not recommended in regions where intestinal parasites may be acquired.
What are some anti-cytokine antibodies?
IL-5 antibody (Mepolizumab) NICE: adults with severe asthma CD25 and IL-2 Antibodies (Daclizumab) Mild improvement in symptoms NICE: already approved in MS (adverse events in liver) IL-25 antibody Reduces Th2 cytokine production in mice In clinical trials IL-9 antibody (MEDI528) Prevents mast cell accumulation in mice Discontinued due to lack of efficacy in humans TNF-alpha antibody (Infliximab) Small trials show improvement in lung function Risk of adverse events (infection, cancer).
What are some ways to prevent mast cell activation?
Membrane stabilisers
Cromones (sodium cromoglycate)
Beta2 agonists
Increase cAMP
Channel blockers
Signalling inhibitors
E.g. Syk kinase, Map kinase inhibitors
Glucocorticoids
Inhibit gene transcription
Some long-term effects
What are some ways to prevent mast cell products?
Histamine receptor antagonists
Numerous target cells
Leukotriene, prostaglandin antagonists
Inhibit activation of Th2 cells
Tryptase inhibitors
Prevent airway smooth muscle activation
Protease-activated receptor (PAR)-2 antagonists
Numerous target cells
How many people get cancer, how many different types of cancer are there?
1 in 3 will get cancer
200 types of cancer, lung, breast, prostate and bowel cancer account for more than half of cases
What is the general feature of tumours?
Tumour express antigens that are recognized as foreign by the immune system of the tumour-bearing host
Immune responses frequently fail to prevent the growth of tumours
The immune system can be activated by external stimuli to effectively kill tumour cells and eradicate tumours
What is the aetiology of cancer?
Transformation of germline cells: inheritable cancers (<10%, Rb, BRCA1, 2)
Transformation of somatic cells: noninheritable cancers (>90%)
Environmental factors:
UV (skin cancer), chemicals (lung cancer), pathogens (HPV causes cervical cancer, helicobacter causes stomach cancer)
What are the hallmarks of cancer?
Growth self-sufficiency
Evade apoptosis
Ignore anti-proliferative signals
Limitless replication potential
Sustained angiogenesis
Invade tissues
Escape immune surveillance
What is tumour immunology?
The immune system has evolved to discriminate self from non-self based on the principle that anything recognised as non-self may be dangerous
The ultimate goal of tumour immunology is to induce clinically effective anti‐tumour immune responses that would discriminate between tumour cells and normal cells in cancer patients
In the relentless pursuit of non-self, our immune systems sometimes work against us
What is the immune system capable of doing?
Immune system is capable of early recognition and elimination of cell in the process of malignant transformation
Mediated by various components of the immune system (T-cells, NKT cells, NK cells)
Scarce evidence for its existence in humans
What is cancer immunosurvelliance?
Immune system can recognize and destroy nascent transformed cells, normal control
What is cancer immunoediting?
Tumours tend to be genetically unstable; thus immune system can kill and also induce changes in the tumour resulting in tumour escape and recurrence
What are the tumour antigens?
Tumour Specific Antigens (TSA)
–Are only found on tumours
–As a result of point mutations or gene rearrangement
–Derive from viral antigens
Tumour Associated Antigens (TAA)
–Found on both normal and tumour cells, but are overexpressed on cancer cells
–Developmental antigens which become derepressed. (CEA)
–Differentiation antigens are tissue specific
–Altered modification of a protein could be an antigen
What is the evidence for tumour immunity?
Spontaneous regression: melanoma, lymphoma
Regression of metastases after removal of primary tumour: pulmonary metastases from renal carcinoma
Infiltration of tumours by lymphocytes and macrophages: melanoma and breast cancer
Lymphocyte proliferation in draining lymph nodes
Higher incidence of cancer after immunosuppression, immunodeficiency (AIDS, neonates), aging, etc.
What is the immune response to tumours?
T lymphocytes
Antibodies
NK cells
Macrophages
What is tumour escape and evasion?
Immune responses change tumours such that tumours will no longer be seen by the immune system: tumour escape
Tumours change the immune responses by promoting immune suppressor cells: immune evasion
What is immunotherapy?
Learn how to harness the immune system to kill tumours: immunotherapy
What are the problems with immunotherapy?
How to kill tumours without killing normal cells?
To induce an immune response against the tumour that would discriminate between the tumour and normal cells: Adaptive immunity
Active immunotherapy
Passive immunotherapy
What is involved with active immunotherapy?
Vaccination
Augmentation of host immunity to tumours with cytokines and costimulators
What vaccines can be used for active immunotherapy?
- Killed tumour vaccine
- Purified tumour antigens
- Professional APC-based vaccines
- Cytokine- and costimulator-enhanced vaccines
- DNA vaccines
- Viral vectors
What is involved with passive immunotherapy?
- Adoptive Cellular Therapy (T cells)
- Anti-tumour Antibodies (Her-2/Neu, CD20, CD10, CEA, CA-125, GD3 ganglioside)
What are the facts about cell-based therapy?
Cellular therapies can be used to activate a patient’s immune system to attack cancer.
They can also be used as delivery vehicle to target therapeutic genes to attack the tumour
They do not act directly on cancer cells. Instead, they work systemically to activate the body’s immune system.
What do dendritic cells do?
Found throughout the body (0.1-0.5%)
Interstitial cells (Liver, heart, liver), Langerhans cells of the epidermis.
Detect and chew up foreign “invader” proteins and then “present” piece of the invaders on their surface.
To make a DC vaccine, the blood of the cancer patient is collected and enriched to increase the population of DC.
What are TAMS?
Tumor-associated macrophages (TAMs), specifically, are often prominent immune cells that orchestrate various factors in the tumor microenvironment
What is involved with tumour hypoxia?
Hypoxia (low oxygen) is a prominent feature of malignant tumours
Inability of the blood supply to keep up with growing tumour cells
Hypoxic tumour cells adapt to low oxygen
What is the problem with tumour hypoxia treatment?
Stimulates new vessel growth
Suppresses immune system
Resistant to radio- and chemotherapy (repopulate the tumour)
Increased tumour hypoxia after therapy
