lecture 3 - TCR and MHC Flashcards
T celld come out the bone marrow and go to the
thymus where the gene segments are rearranged
generation of diversity of TCR
multiple V, D and J gene segments
combinational diversity between V, D and J
junction diversity
does somatic hypermutation happen in TCR
no
TCR alpha chain formation (similar to Ig light chain):
DNA breaks between V and J
random V and J join, then they join to a constant region
TCR beta chain formation (similar to Ig heavy chain):
VD and J regions join and then to a
constant region
what chromosome are TCRalpha genes on
14
what chromosome are the TCRbeta genes on
7
what chromosome is the Ig heavy chain on `
14
what chromosome if the Ig light chain on
2 for kappa
22 for lamda
TCRgamma and YCRdelta form a slightly different receptor.
so a TCR will either be TCR alpha and beta or
TCR gamma and delta
what chromosome is TCR gamma on
7
what chromosome is TCR delta on
14
differences between MHC and TCR/BRC
there no gene rearrangement in MHC molecules
MHC molecules are expressed co-dominantly (MHCs from both chromosomes are expressed)
APC examples
B cells, macrophages, dendritic cells
MHC is located on what chromosome
6
class I MHC molecules are
HLA-A, B and C
class II MHC molecules are
HLA-DP, DQ and DR
HLA-DR has 2
beta chains
MHC are the most polymorphic genes known meaning there’s lots of
alleles
a single cell can have up to how many different MHC molecules
12 (if they are heterozygous for all 6 MHC loci)
where is most of the polymorphism
in the part of the MHC molecule that forms peptide binding groove (alpha 1 and 2)
high levels of polymorphism allows
binding of vast range of peptides that can be presented to T cells
downside with high polymorphism
increase risk of many auto immune mediated disease (e.g. presenting self antigens)
also makes donor organs for transplantation very complex
how do peptides end up bound to MHC molecules
antigen processing and presentation