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Flashcards in TCR Deck (13):

What is the purpose of the TCR

antigen recognition


How is antigen presented to the TCR

via MHC molecules on APCs


Which domains of the TCR make up the antigen recognition site

Va and Vb


How is specificity determined

Each V domain has 3 complementarity determining region loops- Cdr3 is the most variable as this interacts with antigen


How is TCR diversity generated

VDJ recombination
Va is encoded by V and J gene segment in TCRa gene and Vb is encoded by V,D and J gene segments in TCRb gene. one of each of these segments joins to form V chain.
Junctional diversity caused by imprecise joining of fragments increases diversity
Pairing of a and b chains generates combinatorial diversity


How is it ensured that only V and J segments are able to join together

a result of recombinatorial signal sequences which flank the V and J genes. These are different lengths and only 12 and 23 lengths can join together


How is junctional diversity generated

Rag recombinase binds RSS and dimerises bring V and J segments together. the middle part is excised leaving a V and J segment which each have a hairpin loop at the end. the hairpin look is cut at a random site. nucleotides can be trimmed by exonuclease or added in a non-primed manner. single strand ends are filled and coding ends are joined together. this is the site at which CDR3 is found with highest sequence variation.


At what point in T cell development is TCR diversity generated

In the thymus before education


Which other receptors are required for TCR signalling

CD3 and z form part of the TCR complex
CD4 and CD8 are coreceptors of MHC1/2 respectively
CD28 binding in combination with TCR signalling promotes T cell proliferation and differentiation although this is not needed for activation of mature cytotoxic T cells as not all normal cells produce CD28 ligands


what is the effect of CD4+ TCR binding to MHC 2 on B cells and macrophages

B cells are stimulated to produce antibodies and macrophages increase their capacity to kill bacteria


How does granule release by cytotoxic T cells cause cell death

perforin aids granzyme entry through pores in the membrane. There are 4 granzymes produced, all of which are proteolytic enzymes. B causes DNA fragmentation and mitochondrial dysfunction through activation of procaspase 3 and BID resulting in release of proapoptotic factors incl caspase 9.


what is the cause of griscelli syndrome type 2

mutations in Rab27a which disrupt granule exocytosis


what is the cause of FHL2

mutations in perforin