9 - Generation of diversity in T cell receptors - Partridge

Question 1

Which chromosomes are the a /B chain locus located on?

Answer 1

a chain; chromosome 14

B chain; chromosome 7

Question 2

how are the a / B chains similar to the L / H chain gene segments?

Answer 2

a chain corresponds to V and J gene segments on L chain locus.
B chain corresponds to V-D-J regions on H chain locus

Question 3

Draw a diagram that shows the arrangement of the TCR genes on both a / B chain locus

Answer 3

311 - 9

Question 4

How are the TCR genes arranged?

Answer 4

somatic recombination. same recombination machinery as used in B cells used here

Question 5

Where and when does TCR gene rearrangement occur/

Answer 5

occurs in thymus and when the T cells are developing (Ie when acquiring their receptor)

Question 6

What complexes do TCRs recognise?

Answer 6

complex of antigen and self MHC

Question 7

What regions within the Va and B regions recognise the antigen and self MHC?

Answer 7

CDR3 region recognises the antigen. CDR1/2 recognises self MHC (germline encoded)

Question 8

Why does it make sense that CDR3 responsible for binding to antigen?

Answer 8

CDR3 regions show most variability. correspond to V-J OR V-D-J join. we have junctional variability here (activity of TdT)

Question 9

Describe the 3 ways we get diversity of the TCR genes

Answer 9

1) multiple copies of each Variable region gene segment. (Vn x Jn) / (Vn x Dn x Jn)
2) combination of a and B chains. (Va x Ja) x (VB x DB x JB)
3) junctional diversity. concentrated to CDR3s of a and B chains

Question 10

V regions of TCRs do NOT undergo _____ ______ once T cells enter the peripheral lymphoid tissue

Answer 10

somatic hypermutation

Question 11

What is the 2nd T cell subset called and what % of T cells are this type?

Answer 11

gamma delta (γδ) subset 
around 1-5% T cells

Question 12

How is the diversity in γδ T cells generated?

Answer 12

gene rearrangement although fewer V region gene segments. junctional variability may compensate.

Question 13

Where are these γδ cells found?

Answer 13

in the mucosal epithelium. majority of infections happen here. may play similar role to IgA antibody?

Question 14

Overall, describe these γδ cells

Answer 14

• do not require processing and presentation of the antigen by MHC. receptors more Ab like - recognise broader range of antigens (eg lipids). respond to effects of infection rather than the pathogen itself