T-cell Receptor Overview

Alpha-Beta Heterodimer

More common TCR, recognizes Ag peptides on MHC I or II

Gamma-Delta Heterodimer

Less common TCR, doesn’t require antigen presentation

TCR chains

Members of Ig superfamily, have 2 Ig-like domains with intrachain disulfide bond, C and V regions (with 3 CDR regions)

TCR transmembrane region

Usually hydrophobic but has positively charged amino acid residues that interact with negatively charged residues on CD3 complex, short cytoplasmic tail

RAM

Receptor associated molecules for TCRs, the CD3 component, 3 dimers

CD3 dimers

epsilon delta, epsilon gamma, and zeta zeta or zeta eta

Zeta-Zeta dimer

Has the most phosphorylation sites (3 each, 6 total), where the others only have two total

RAM functions

Have ITAMs in cytoplasmic domain, phosphorylation, docking for adapter proteins, have negative charged amino acid residues in transmembrane region that interacts with positive charged residues of TCR heterodimer (alpha-beta)

CD4

Monomer with 4 Ig-like domains and disulfide bonds, each has a hydrophobic transmembrane domain and their cytoplasmic tail (serines) can be phosphorylated, guides MHCII to TCR

CD8

alpha beta heterodimer, with one Ig-like domain and disulfide bond, has hydrophobic transmembrane domain and tail has several residues that can be phosphorylated

T-cell co-receptor (CD4 or CD8)

Binds MHC to increase avidity of T-cell and target antigen binding

CD28

Another T-cell co-receptor, binds CD80 and/or CD86 on APC for full activation of naive T-cell