Immunology 7-9 Flashcards
What are naive T cells?
Recirculating lymphocytes that have not yet encountered their specific antigen.
When is T cell-mediated immunity required?
When antibodies are not sufficient to clear the infection.
Why is T-cell mediated immunity sometimes needed?
- Pathogens can be intracellular and hide within cells (HIV, TB and malaria)
- Can evolve to escape antibody recognition by changing shape, coating antigens in carbohydrates or producing decoy antigens.
Where is an intracellular pathogen processed?
Cytosol
Where is an extracellular pathogen processed?
Endosomes
What do CD8 cells do?
Destroy target cells by recognising MHC I. Recognition results in polarisation of cytotoxic vesicles in the cell, inducing apoptosis.
What do cytotoxic granules often have in them?
Granulysin, granzymes and perforin.
What can T helper cells do?
A.k.a CD4+ cells
- Macrophage activation (increases CD40 and TNF-alpha secretion, synergising with interferon)
- Delayed type 1 hypersensitivity
- B cell activation
- Regulation
What do Th1 cells do?
Produce interferon-gamma, IL-12 and TNF-alpha. Pro-inflammatory and boosts intracellular immune responses.
What do Th2 cells do?
Produces IL-4, 5 and 13. Pro-allergenic and boosts anti-multicellular organism response).
What do Th17 cells do?
Secrete IL-17, 23 and 6. Prevents bacterial growth. Pro-inflammatory.
What do Tfh cells do?
Follicular T helper cell. Produces IL-21. Essential for isotype switched antibodies.
What do Treg cells do?
Regulate activation of T cells (natural or induced). Anti-inflammatory. Produces IL-10 and TNF-alpha.
How do memory cells differ from T cells?
- Proliferate faster
- Less strict activation
- Express different chemokine receptors
What does TNF stand for?
Tumour necrosis factor
What causes autoimmune diseases?
Susceptible genes and environmental triggers - a fundamental imbalance between immune activation and control.
How are immune responses controlled?
- Response declines as pathogen is eliminated due to apoptosis of lymphocytes once they have fulfilled their role and lost their survival signal.
- Active control functions limit response to persistent pathogens to prevent excessive tissue damage.
What is immunological tolerance?
Specific unresponsiveness to persistent antigens that is induced by exposure of lymphocytes to that antigen.
What is central tolerance?
Destroying self-reactive B or T cells before they enter the circulation.
What is peripheral tolerance?
Destroying or controlling self-reactive B or T cells once they have entered the circulation.
What is meant boy nTreg?
Natural regulatory T cells that reside in peripheral tissues to prevent harmful reactions against “self” from occurring.
What is meant by iTreg?
Inducible regulatory T cells that develop from mature CD4+ cells once exposed to a foreign antigen in the periphery.
When are iTreg cells generated?
In all immune responses to limit tissue damage.
What is IL-10?
Known as the master regulator - anti-inflammatory cytokine. Acts on a range of cells, blocking pro-inflammatory cytokine synthesis. Downregulates macrophages.
What do type I and III interferons do?
- Activate NK cells
- Upregulate MHC
- Activate RNase
- Induce anti-viral state
What do type II interferons do?
Pro-inflammatory cytokines.
How do influenza and RSV differ?
- No vaccine for RSV
- Reinfection with RSV enhances infection (vaccine enhanced disease)
- Can be reinfected with same strain of RSV but not influenza
- Vaccine for influenza constantly needs updating due to different strains evolving
