🌞 T Cell Receptor and MHC

Question 1

How is T cell receptor (TCR) diversity generated?

Answer 1

random gene rearrangement

Question 2

What is the structure of a T cell receptor?

Answer 2

a + b chains
a → V J C gene segs
b → V D J C gene segs

Question 3

How do T cells recognise antigen?

Answer 3

TCRs recon processed, internal peptides pres by APC on MHC

~ Fab region of BCR

Question 4

What is the role of MHC molecules?

Answer 4

pres processed Ag → T cells → active + diff

Question 5

What is the difference between MHC class I and MHC class II?

Answer 5

Class 1 (HLA-A -B -C) → pres to CD8+
Class 2 (HLA-DR -DP -DQ) → pres extracell peptidesto CD4+

Question 6

Which cells express MHC I and which express MHC II?

Answer 6

MHC1 → all nucleated cells → pres endogenous peps → CD8+ t cells

MHCII → prof APCs only (DCs, MPs, B cells) → pres exogenous peps → CD4+

Question 7

What kind of antigen is presented on MHC I vs MHC II?

Answer 7

MHC1 → endogenous e.g. viral/tumour Ps
MHC2 → exogenous e.g. bact, toxins

Question 8

Which T cell subsets recognise MHC I and MHC II?

Answer 8

cd4+ T cells → recog MHC2
cd8+ T cells → recog MHC1

Question 9

What co-receptors do CD4+ and CD8+ T cells use?

Answer 9

TCR binds peptide/MHC via complementarity determining regions (CDRs)

Cd4+ → use CD4 co-recep → binds MHCII
CD8+ → use CD8 co-recep → binds MHCI

Question 10

Why is antigen processing necessary for T cell activation?

Answer 10

T cells only recognise short + linear pep frags

Question 11

Where are antigens processed for loading onto MHC I and MHC II?

Answer 11

MHC1 → pep processed in cytoplasm → loaded onto MHCI in ER

MHC2 → pep processed in endosome/lysosome → loaded onto MHCII in endosomal comparetments