Genetics Of Tcr /mch

Question 1

Where does gene rearrangement in the ab tcr heterodimer occur

Answer 1

Thymus during development there

Question 2

How does gene rearrangement occur in tcr

Answer 2

Same as bcr. Rag genes and rag complex such as recombinase cleave at RSS and then ligate the gene segments

Question 3

Do a and b heterodimer tcr have combinatorial and junctional diversity (tdt) like bcr

Answer 3

Yes

Question 4

What are the diff between tcr and bcr

Answer 4

Tcr never gets secreted

It doesn’t undergo somatic hypermutation via aid c to u deamination

Develops in thymus not bone marrow

Question 5

Does tcr have constant region isotypes like the Heavy ig chain

Answer 5

No

Question 6

How is the tcr a gene arranged and what chromosome

Answer 6

Chromosome 14

Has many Va then 5 Ja regions followed by Ca (constant region)

Question 7

How is tcr b chain arranged (similar to heavy chain on bcr) and what chromosome is it on

Answer 7

Chromosome 7

Vb , then Db, then Jb followed by Cb constant region

Question 8

What chromosome is Tcr y on and what gene segments does it have

Answer 8

On chromosome 7

Has v and j

Question 9

What chromosome is tcr delta on with vdj segments

Answer 9

Chr14

Question 10

Does gene rearrangement occur in mhc

Answer 10

No

Question 11

What chromosome are MHC genes on

Answer 11

6

Question 12

MHC alleles are co dominantly expressed. How is this diff to bcr and tcr

Answer 12

In bcr and tcr they undergo allele exclusion. After rearrangement occurs in 1 chromosome recombination machinery turned off. Means only 1 receptor type on a cell

Question 13

What is bcr and tcr allele exclusion called

Answer 13

They are clonally distributed

Question 14

What upregulates MHC II which presents to CD8 T cells

Answer 14

Cytokines like ifn

Question 15

What are the 3 genes/molecules of class I mhc

Answer 15

Hla a , hla b , hla c (all 3 on chr6 encode the A1,2,3 domains)

Question 16

What are the 6 genes for class II

Answer 16

Dp a, b

Dq a,b

Dr a,b

Question 17

Other than the 6 main genes for MHC II. What other gene is important for presentation

Answer 17

Hla DM a and b

Question 18

What does MHC polymorphism mean

Answer 18

Many alleles for the genes such as hla dr B gene has many alleles causing presentation of diff peptides

Question 19

Which class of MHC is more polymorphic

Answer 19

Class I hla a b and c

Question 20

If a person is heterozygous at each loci of class I. How many diff MHC can they have

Answer 20

6 (because 3 types of MHC 1)

Question 21

If a person is hz at each loci, how many class II could they express

Answer 21

Also 6 because 3 types of MHC II

Question 22

MHC because they are co dominant are polymorphic What does this mean

Answer 22

All slightly different ie different peptides

Question 23

Where are most polymorphisms

Answer 23

In peptide binding cleft

Question 24

How can MHC polymorphism cause auto immunity

Answer 24

Can virtually bind to any peptide which could be self peptide and cause autoimmune response via activating T cells

Question 25

How does MHC cause organ rejection

Answer 25

The polymorphisms mean people have different MHC which will be detected as foreign by the donor or recipient causing immune response