Immunology Flashcards
There exists an evolutionary arms race between pathogen and host. What does this mean?
Pathogen exploits flaws in the defensive barriers of its host The host evolves to correct those flaws Pathogen replicates and evolves to evade corrections to exploit other flaws Pathogen has ability to replicate much faster than the host; host relies on flexible and rapid immune response to combat
Some features of skin that contribute to barring infection include…(3)
Tightly packed keratinised cells undergo renewal constantly; limits colonisation
Low pH kills pathogens
Sebaceous glands secrete oils and enzymes to destroy bacterial cell walls
Some features of mucous that contribute to barring infection include…(4)
Directly traps pathogens in body lining
Secretory IgA prevents bacteria and viruses penetrating epithelial cells
Contains enzymes - lysozyme, defensin, anti-microbial proteins, lactoferrin
Contains cilia - help remove mucous
The innate immune system has a ___ response and is ____ to micro-organisms
Fast, non-specific
The adaptive immune system has a ___ response and is ____ to micro-organisms
Slow, specific
The 5 types of leukocytes (WBCs)?
Neutrophils, Monocytes, Lymphocytes, Eosinophils, Basophils + Mast cells
Primary lymphoid tissue?
SITE OF LEUKOCYTE DEVELPMENT: Bone marrow, thymus
Secondary lymphoid tissue?
ADAPTIVE IMMUNE RESPONSE: Spleen, tonsils (any sites of AIS activation), lymph nodes
List the leukocyte components of the innate immune system
Macrophages, neutrophils, dendritic cells, basophils, mast cells, eosinophils, NK cells
List the protein components/humoral factors of the innate immune system
Complement, acute phase, cytokines
Role of cytokines
Includes INFs, ILKs, TNFa, pro-inflam chemokines: Modulate the behaviour of cells, locally and systemically by binding to receptor on target cell
Role of NK cells
Large granular lymphocytes that kill tumours and infected cells
Role of mast cells, eosinophils and basophils
Highly granular cells, reside in tissues and protect mucosal surfaces, release chemicals, recruited via inflam signals
Basophils and mast cells mature in bone marrow. True/false?
False Basophils mature in bone marrow; mast cells mature once in tissue
Basophils and mast cells are mainly involved in ____. They secrete ____, leading to _____…
Allergic reactions
Secrete histamine and inflammatory mediators (DEGRANULATION),
leading to increased vascular permeability and smooth muscle contraction (GENE EXPRESSION - increase new proinflam mediators)
The main function of phagocytes is? Main types?
"Eat" cells by ingesting them and mopping up debris -Neutrophils (short lived, most numerous) Macrophages (long lived) Dendritic cells (AP to T cells) PHAGOCYTOSIS
PRRs recognise what on bacteria/viruses?
PAMPs
Not expressed by human cells
Opsonins enhance…
Phagocytosis
Act as a bridge between pathogen and phagocyte receptors
Major opsonins include…
C3b, collectins, Fc of IgG/IgM, CRP
Acute phase proteins (inc. CRP) are produced by…
The liver
CRP greater than 200mg/l indicates…
Severe bacterial/fungal infection
Oxidative killing requires which crucial enzyme?
Alternative option in phagocytosis?
NADPH oxidase complex - Converts oxygen into reactive free radicals
Via anti-microbial proteins
Interferons are important in…
Limiting viral infections
Interleukins are important in…
Directing cells to divide/differentiate Mainly produced by T cells (IL-2 important for T cell activation)
Chemokines are important in…
Establishing a concn gradient to direct movement of cells (tell leukocytes where to go)
List the main components of pus…(4)
Neutrophils, NETs (neutrophil traps that immobilise the pathogen), dead bacteria, cellular debris
Complement involves enzymatically activating proteins in a…
Types of pathways (3)…
Biological cascade, resulting in a rapid response - classical, mannose-binding lectin or alternative pathway
Classical pathway is activated by…
Antibodies (so B cells need to have been activated for this) IgG/IgM cause conformational change in C1, activating cascade
In the classical pathway, first C1 is activated, then…
C4, C2, C3
Lectin pathway is activated by…
Mannose-binding lectin binding to carbohydrates This mimics binding of C1 to immune complexes, so there is no need for antibodies
Alternate pathway is activated by…
Spontaneous hydrolysis of C3 and its direct binding to bacterial cell walls — C3a and C3b —- C5 — C5a and C5b
Membrane attack complex is assembled by which complement proteins?
C5-C9
Functions of C3a and C5a
Inflammatory mediators - recruit phagocytes
Examples of complement inhibitors
C1, Factor I, Factor H, C4 binding protein, CD59
List the leukocyte components of the adaptive immune system
B lymphocytes, T lymphocytes
List the protein components/ humoral factors of the adaptive immune system
Antibodies, cytokines
Give the main role of B cells
Protect against intercellular pathogens via antibodies
Give the main role of T cells and active types
Protect against intracellular pathogens and split into CD4 + T helper cells - key regulators of immune system
CD8 + T cells (CTLs) - kill virally infected body/cancer cells
Antibodies act as opsonins. True/False?
True
Antibodies are Y shaped glycoproteins made up of…
Chains held together by…
Two heavy chains and two light chains
Heavy chains have variable regions (antigen binding site); light chains have constant regions
Disulphide bridges
T cell antigen receptors can recognise free antigens. True/False?
False Need to be presented as a complex with MHC molecules
MHC I presents to?
CD8+ T cells Expressed on all nucleated cells
MHC II presents to?
CD4+ T cells Expressed only on antigen presenting cells (dendritic cells, B cells, macrophages)
T cell activation requires…
MHC binding to T-cell receptor B7 binding to CD28
B cell activation requires…
Antigen binding to B-cell receptor PRRs recognising PAMPs Optional co-stimulation by CD4+ cells through CD40L
List the consequences of T and B cell activation
7-10 days - mitosis —- clonal expansion and differentiation into effector or memory cells
List the immunoglobulins found in the blood, from most to least abundant
IgG, IgA, IgM, IgD, IgE
Main function of IgG
Provides antibody-mediated immunity to developing foetus and neonates
Main function of IgA
Secretory; found in breast milk, saliva, tears
Defence at mucosal surfaces
Main function of IgM
Found in blood; first Ig produced during infection
Main function of IgD
Unknown; protection against URT infections
Main function of IgE
Activates mast cells (causes degranulation)
Function of IL-2
Activates CD8+ cells
Function of IL-2
Suppresses the immune response
Function of IL-4, IL-5 and IFNy
Activate B cells; increase killing
4 different types of memory cells
Helper T-cells
B-cells
Cytotoxic T-cells
Long lived plasma cells
Name some pro-inflammatory cytokines
IL-1 IL-6 TNF
What effect do pro-inflammatory cytokines such as IL-6 have on the liver?
Stimulate release of acute phase proteins (CRP, C3…)
Give the action of CTL and the chemicals used in this response (3)
CTL from CD8 binds to MHC1 receptor causing DNA fragmentation and cell death
PERFORIN: polymerase to form pore in target membrane
GRANZYME: activate apoptosis once in target cell cytoplasm
GRANULYSIN: induce apoptosis
