CO-RECEPTORS OF B-LYMPHOCYTES

The past year has seen advances in our understanding of accessory memb rane proteins that modulate the B cell response to antigen-receptor st imulation. The generation of complement receptor deficient mice has re inforced our appreciation of the importance of complement receptors in the B cell response to antigen. The association of inositol polyphosp hate B-phosphatase with Fc gamma RIIB suggests another mechanism; in a ddition to recruitment of the phosphotyrosine phosphatase SHP-1, by wh ich secreted immunoglobulin can limit further response to antigen. The in vivo function of CD22 in regulating the threshold of antigen-recep tor signalling has been shown using CD22-deficient mice. Lastly, B cel l receptor signalling in the B-1 subset of B lymphocytes has been demo nstrated to be negatively regulated by CD5.