T-cell and B-cell receptors (TCR, BCR)

The T-cell receptor is a membrane-bound protein complex mainly composed of alpha (α) and beta (β) chains, with rare forms containing gamma (γ) and delta (δ) chains. Its variable regions provide unique antigen specificity, and signal transduction is mediated by the CD3 complex containing ITAMs. Upon antigen recognition (as peptide-MHC), the TCR triggers immune responses including cell-mediated cytotoxicity (by cytotoxic T cells), helper functions (by helper T cells), and memory formation. The B-cell receptor is a multiprotein complex comprising membrane-bound immunoglobulin (antibody) molecules (with variable heavy and light chains) associated with Igα/Igβ (CD79a/CD79b) signaling modules. BCRs recognize soluble antigens and can mediate antigen processing, presentation, and signaling events leading to B cell activation, differentiation into plasma and memory cells, and antibody production. Both complexes share evolutionary and structural similarities, utilize ITAM phosphorylation for initiating signaling, and play critical roles in the adaptive immune response. Although discussed together here, it is important to note that these are distinct molecular complexes and should ideally be treated separately.

Other names

TCRBCRmembrane-bound immunoglobulinTCRαβTCRγδ

Inhibition of antigen receptor signaling (e.g., kinase inhibitors blocking downstream pathways); Reduction of lymphocyte proliferation and activation; Induction of apoptosis in malignant or autoreactive lymphocytes; Modulation of cytokine secretion.