T cells, effector functions and MHC

Question 1

MHCI structure; where is it expressed; how does it work

Answer 1

single alpha-chain that associates with beta-2-microglobulin non-covalently;
expressed endogenously on all nucleated cells;
virus infects cell-> hijacks protein production machinery-> host cell breaks down a sample of all proteins produced in a cell (proteosome) on RER-> load onto MHCI-> present at cell surface

Question 2

MHC II structure; where is it expressed; how does it work

Answer 2

alpha-beta heterodimer
expressed on APC eg monocyte/macrophage/dendritic cell/b cell
fusion with bacterial antigens after phagocytosis

Question 3

polymorphisms in MHC genes implications

Answer 3

these determine the aa that form peptide binding groove and what MHCs will present
each MHC has many gene variants-> codominant expression possible

Question 4

tcr structure

Answer 4

heterodimer
two types: alpha-beta; gamma-delta
each chain has 1 varaible and 1 constant domain
variable domain comes from genes that undergo rearrangements from germline before translation

Question 5

what kind of signals cause upregulation of co-stimulatory molecules (CD 28 AND 86)

Answer 5

infection

inflammation

Question 6

what happens when T cells are activated

Answer 6

proliferation

cytokine production

Question 7

what happens when CD4 is activated into Th1?

Answer 7

releases IFN-gamma-> activation and differentiation of macrophages
releases IL2+ IFN-gamma-> CD8 differentiates and proliferates

Question 8

what happens when CD4 is activated into Th2?

Answer 8

th2 produces IL2/IL4/IL5/IL13
this promotes for b cells…
cell division/class switching/affinity maturation/differentiation into plasma cells/parasite clearance by activating eosinophils

Question 9

what happens when CD4 is activated into Th17?

Answer 9

th17 produces IL17/IL21/IL22
helps epithelium/fibroblasts secrete antimicrobial peptides-> aid wound healing
attract neutrophils to infection site