CD22 REGULATES THYMUS-INDEPENDENT RESPONSES AND THE LIFE-SPAN OF B-CELLS

THE B-lymphocyte-restricted glycoprotein CD22 is expressed on mature I gM(+) IgD(+) B cells(1-3), and is capable of binding to ligands on T a nd B cells(2,4-7). CD22 can interact with both the B-cell antigen rece ptor (BCR) complex(8,9) and signalling molecules, including the protei n tyrosine phosphatase SHP1 (PTP1C, SHP)(10-12), a putative negative r egulator of BCR signalling(13,14). Thus CD22 may facilitate interactio ns with lymphocytes and regulate the threshold of BCR signalling(1,11, 13). To define the in vivo function of CD22, we generated CD22-deficie nt mice. Here we show that CD22 is required for normal antibody respon ses to thymus-independent antigens and regulates the lifespan of matur e B cells.