T cell Receptor

MAJOR DIFFERENCESBETWEEN TCR AND Ig GENES• Somatic hyper-mutation (affinity maturation)- During an antibody response, mutations accumulate at arapid rate in the VDJ gene segments encoding the BCR.- Thus, as an immune response proceeds, the affinity of theantibody produced (i.e. its ability to bind to the antigen)increases.• Alternative joining of D segments (β, δ)• N-nucleotide addition to both chains***1.6 x 10 11 VS 3 x 10 7Properties of Ig and TCR GenesIg TCRMany VDJs, few Cs yes yesVDJ rearrangement yes yesV-regions form antigen yes yesrecognition siteSomatic hypermutation yes noProperties of Ig and TCRProteinsIg TCRTransmembrane forms yes yesSecreted forms yes noIsotypes with different yes no*functionsValency 2 1The TCR complex includes CD3 - 3 heterodimers: γε, εδ and ζζ- 1) TCR is not expressed without CD3. It is required to bringTCR to surface- 2) All chains of CD3 possess ITAM motifs. (Immunoreceptortyrosine-based activation motif) Signal TransductionTCR Receptor Complex- CD3RECOGNITIONSIGNAL TRANSDUCTION4