B cell receptors and MHC class II molecules (BCR (B cell receptor) MHC class II (Major histocompatibility complex class II molecule))

B cell receptor is a clonally unique antigen receptor on the surface of B cells, responsible for recognizing specific antigens and initiating B cell activation, proliferation, and differentiation. After antigen binding and internalization, the BCR-antigen complex is processed, and antigenic peptides are loaded onto MHC class II molecules within specialized endosomal compartments. B cells then present these peptides on MHC class II at their surface, enabling recognition by CD4+ T cells. This BCR/MHC class II "axis" is essential for humoral immunity, germinal center formation, antibody production, and affinity maturation[4][5][7][8]. MHC class II molecules are heterodimeric glycoproteins expressed on antigen-presenting cells (especially B cells, dendritic cells, macrophages). They present processed antigenic peptides to CD4+ T helper cells, launching critical immune responses. MHC class II expression and function is regulated, including via the invariant chain and accessory molecules such as HLA-DM and HLA-DO, and is crucial for self-tolerance as well as response to infection and cancer[3][5][7][8]. Both B cell receptors and MHC class II molecules are implicated in immune-mediated disease and cancer, and are important targets for immunomodulatory and cytotoxic therapies[1][3][5][8].

Other names

BCRimmunoglobulin receptormembrane-bound immunoglobulinHLA-DRHLA-DQHLA-DP (in humans)I-AI-E (in mice)MHC IIclass II histocompatibility antigen

MHC Class II targeting drugs: Block or deplete MHC class II-expressing cells (antibody-dependent cell cytotoxicity or direct signaling-induced apoptosis). B cell receptor targeting drugs: Inhibit BCR signaling pathways (BTK inhibition), Deplete BCR-expressing cells (anti-CD20).