Activation of human B cell proliferation through surface Bp35 (CD20) polypeptides or immunoglobulin receptors.
Human B cells can be activated with monoclonal antibodies (mAb) to surface IgM receptors or mAb to a 35-kilodalton B cell differentiation antigen, Bp35 (CD20). We compared anti-Ig-induced B cell activation with B cell triggering by anti-Bp35. Both anti-Ig- and anti-Bp35-dependent proliferation were augmented by the same co-stimulants, including a partially purified BCGF, recombinant IL 1, TPA, or each other. When anti-Bp35 and anti-Ig were used together to induce proliferation of tonsillar B cells, the strongest response was observed when anti-Bp35 was added 12 to 24 hr before anti-Ig. Anti-Bp35 also was found to act most effectively when added before the BCGF. Blood and tonsillar B cells differed in their proliferative response to anti-Ig or anti-Bp35: unlike dense tonsillar B cells, which consistently proliferated in response to either stimulus, blood B cells from many donors proliferated in response to anti-Ig but not to anti-Bp35 even in the presence of other co-stimuli. Dense tonsillar B cells that proliferate in response to anti-Bp35 appeared to be at a more activated stage than unresponsive blood B cells because they expressed higher levels of HLA class II molecules than blood B cells. Pretreatment of blood B cells with anti-Bp35 converted them to an HLA-DR(bri) phenotype and made them more responsive to anti-Ig-induced proliferation. These results suggest that B cells at different stages of differentiation differ in their response to anti-Bp35 and anti-Ig. The Bp35 surface polypeptide may play an early role in the activation of B cells prior to antigen or other signals.
D000906:Antibodies / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D006133:Growth Substances / Q000494:pharmacology; D006684:HLA-DR Antigens / Q000032:analysis; D006801:Humans; D007211:Indoles / Q000276:immunology*; D015847:Interleukin-4; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000494:pharmacology; D014066:Palatine Tonsil / Q000276:immunology; D011961:Receptors, Fc; D011971:Receptors, Immunologic / Q000276:immunology*
D000906:Antibodies; D000911:Antibodies, Monoclonal; D006133:Growth Substances; D006684:HLA-DR Antigens; D007211:Indoles; D008222:Lymphokines; D011961:Receptors, Fc; D011971:Receptors, Immunologic; C035311:immunoglobulin M receptor; D015847:Interleukin-4; C042610:5-bromo-4-chloroindoxyl acetate