BCRcoreceptor
BCR co-receptor refers to a multi-protein complex that associates with the B cell receptor (BCR) to modulate and amplify signaling during antigen recognition. The primary components of the BCR co-receptor are CD19, CD21 (CR2), and CD81 (TAPA-1). This complex is expressed on mature B cells and interacts with the BCR to tune its response to antigen.
CD21 binds the complement fragment C3d on opsonized antigens, bringing the antigen into close proximity with
Functionally, the BCR co-receptor enhances B cell activation, proliferation, and antibody production, and supports germinal center