Week 4 Practise Questions L9-10

Question 1

What are the signals required for activation of “naïve” T cells?

Answer 1

Signal 1 (antigen + MHC + CD4/CD8), Signal 2 (co-stimulation e.g. between B7 and CD28), Signal 3 (cytokines that determine which “subset” of T helper cells is produced)

Question 2

How are TH2 T cells induced and how do they act?

Answer 2

Induced by IL4 (produced by antigen presenting cells in response to parasitic infection), produce IL4, IL5, IL13, activate mast cells, basophils, eosinophils, promote production of IgE. Improtant in extracellular parasitic infections and allergy.

Question 3

Describe the properties of 2 other T helper subsets. How do the subsets facilitate the immune response?

Answer 3

Two from TH1 cells (important in intracellular infections, extracellular microbe infections), TH17 cells (important in bacterial/fungal infections at mucosal surfaces), TFH cells (promote B cell class switching), TREGS (important in preventing autoimmunity, downregulating immune responses)

Question 4

What are stages involved in killing of infected cells by cytotoxic T cells?

Answer 4

Specifically bind to cells displaying foreign peptide + MHCI, produce perforin channels, granzymes enter infected cells and initiate apoptosis.

Question 5

How do γδ T cells differ from αβ T cells?

Answer 5

They express different TCRs (γδ), are generally less diverse at the genetic level, recognise a broader range of antigens, do NOT require antigen presentation via MHCI/II, arise earlier in development, are mainly found at mucosal surfaces

Question 6

What abnormalities might be expected in an individual who deficient in CTLA-4?

Answer 6

CTLA-4 binds B7 to “de-activate” T cells, so would expect patients to be more prone to autoimmunity and excessive inflammation.