B-cell receptor; T-cell receptor (BCR; TCR)

The **B-cell receptor (BCR)** is a transmembrane receptor complex found on the surface of B lymphocytes, composed of a membrane-bound immunoglobulin molecule for antigen binding and associated invariant signaling proteins (Igα/Igβ, also known as CD79a/CD79b). The BCR is essential for antigen recognition, B-cell activation, differentiation, and antibody production. The **T-cell receptor (TCR)** is a transmembrane protein complex present on T lymphocytes, formed by clonally variable α/β or γ/δ chains that recognize processed antigen fragments in the context of MHC molecules. Accessory proteins (the CD3 complex and ζ chains) mediate signal transduction, leading to T-cell activation, expansion, and effector function. Both receptor systems mediate signal transduction via immunoreceptor tyrosine-based activation motifs (ITAMs) and trigger the adaptive immune response by initiating lymphocyte activation, proliferation, and differentiation[1][3][4][6][7][10].

Other names

B-cell antigen receptorT-cell antigen receptorantigen receptorimmunoglobulin receptor (for BCR)

- Inhibition of kinase activity (e.g., BTK, SYK inhibitors in BCR pathway) - Blockade of co-receptor signaling (e.g., CD3 antagonists for TCR in transplantation) - Modulation of downstream effectors to prevent lymphocyte proliferation or differentiation