Genetics Of Tcr /mch Flashcards
Where does gene rearrangement in the ab tcr heterodimer occur
Thymus during development there
How does gene rearrangement occur in tcr
Same as bcr. Rag genes and rag complex such as recombinase cleave at RSS and then ligate the gene segments
Do a and b heterodimer tcr have combinatorial and junctional diversity (tdt) like bcr
Yes
What are the diff between tcr and bcr
Tcr never gets secreted
It doesn’t undergo somatic hypermutation via aid c to u deamination
Develops in thymus not bone marrow
Does tcr have constant region isotypes like the Heavy ig chain
No
How is the tcr a gene arranged and what chromosome
Chromosome 14
Has many Va then 5 Ja regions followed by Ca (constant region)
How is tcr b chain arranged (similar to heavy chain on bcr) and what chromosome is it on
Chromosome 7
Vb , then Db, then Jb followed by Cb constant region
What chromosome is Tcr y on and what gene segments does it have
On chromosome 7
Has v and j
What chromosome is tcr delta on with vdj segments
Chr14
Does gene rearrangement occur in mhc
No
What chromosome are MHC genes on
6
MHC alleles are co dominantly expressed. How is this diff to bcr and tcr
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
What is bcr and tcr allele exclusion called
They are clonally distributed
What upregulates MHC II which presents to CD8 T cells
Cytokines like ifn
What are the 3 genes/molecules of class I mhc
Hla a , hla b , hla c (all 3 on chr6 encode the A1,2,3 domains)
What are the 6 genes for class II
Dp a, b
Dq a,b
Dr a,b
Other than the 6 main genes for MHC II. What other gene is important for presentation
Hla DM a and b
What does MHC polymorphism mean
Many alleles for the genes such as hla dr B gene has many alleles causing presentation of diff peptides
Which class of MHC is more polymorphic
Class I hla a b and c
If a person is heterozygous at each loci of class I. How many diff MHC can they have
6 (because 3 types of MHC 1)
If a person is hz at each loci, how many class II could they express
Also 6 because 3 types of MHC II
MHC because they are co dominant are polymorphic What does this mean
All slightly different ie different peptides
Where are most polymorphisms
In peptide binding cleft
How can MHC polymorphism cause auto immunity
Can virtually bind to any peptide which could be self peptide and cause autoimmune response via activating T cells
How does MHC cause organ rejection
The polymorphisms mean people have different MHC which will be detected as foreign by the donor or recipient causing immune response
