6A: Immune system & Infection Flashcards
1
Q
Microbial factors
A
- Type of organism (e.g. virus, bacterium, parasite)
- Dose (degree of exposure)
- Virulence
- Route of entry
2
Q
Host factors
A
- Integrity of innate barriers
- Adaptive immune competence
- HLA, Ig & TCR genes
- Previous exposure
- Other infections
3
Q
Viruses
A
- Lytic or integrated cycle
- Capsid antigens
- Internal structural components (HLA)
- Metabolic products (HLA)
4
Q
Bacteria (& fungi)
A
- Extracellular (e.g. S. aureus) or intracellular (e.g. M. tuberculosis)
- Structural components
- Metabolic products & toxins
5
Q
Parasites
A
- Large (multicellular) (slower)
- Life cycle changes
- Radical changes in antigenicity
6
Q
Antibody structure
A
- 2 light chains
- 2 heavy chains joined with disulphide bonds at hinge region
- Hypervariable regions on light chains
- Complement-binding region
- Fc region (links to receptors)
7
Q
5 classes of antibodies
A
- IgM – first in primary response, large, mostly in bloodstream
- IgG – second in primary response, dominates secondary response, most abundant, in most body fluids
- IgA – high in mucus, surface protection
- IgE – associated with basophils & mast cells, allergies, (parasites)
- IgD – surface reception of naïve antigen-sensitive B cells
8
Q
Cytotoxic T lymphocytes
A
- Viral peptide is presented by HLA class I
- Cytotoxic T cell recognises HLA class I & binds, killing the target cell
9
Q
Immune factors
A
- Direct neutralisation by antibodies
- Opsonisation & phagocytosis
- Complement-mediated effects
- HLA-restricted T cell-mediated cytotoxicity
- NK cell-mediated cytotoxicity
- Inflammatory & regulatory cytokines
- Antiviral cytokines (e.g. interferons)
10
Q
Antibodies: Effective against antigens outside cells of body
A
- Viruses (IgA, IgG, IgM)
- Toxins (IgG, IgM)
- Extracellular bacteria (IgA, IgM, IgG)
- Parasites (IgE, IgA)
11
Q
Cytotoxic T cells: Effective against intracellular protein antigens
A
- Virus infections (cytoplasmic peptides)
- Tumour cells
- Transplanted organs
12
Q
Immunity to bacteria
A
Antibodies & complement:
- Enhance bacterial destruction
- Enhance phagocytosis (opsonisation)
Bacterial resistance:
- Capsule resists opsonisation (e.g. Haemophilus influenzae)
+ Slippery capsule of Haemophilus influenza avoids them being eaten by neutrophils
- Intracellular growth
13
Q
Antibodies around birth
A
- When utero baby has maternal antibodies (IgG)
- After birth maternal antibodies decrease and Childs own antibodies develops
14
Q
Interferon antiviral mechanism
A
- Interferons send signals from virus infected cells to uninfected cells so the uninfected cells can protect themselves from the virus
- Interferons activate Natural Killer cells to seek out & kill virus cells more effectively
15
Q
Cytokines in infection
A
Proinflammatory (IL-1, IL-6, TNF-a) - Early, induce acute phase proteins - Temperature (fever) & behavioural changes - TNF-a triggered by bacterial LPS - Tissue repair: \+ Bone resorption \+ Fibroblast proliferation \+ Collagenase synthesis \+ Leukocyte adhesion - T & B cell activation
Chemokines:
- Aid chemotaxis (e.g. neutrophils)
- Direct effector cell traffic
Interferons:
- Induce transient antiviral state
- Activate NK cell activity
- Upregulate HLA expression (improves cytotoxic T cell killing)
