title: Activation of human B cells mediated through two distinct cell surface differentiation antigens, Bp35 and Bp50.
abstract: Two human B-cell differentiation antigens, Bp35 and Bp50, apparently play distinct roles as signal receptors in B-cell activation. Monoclonal antibodies (mAbs) to either Bp35 or Bp50 deliver positive signals to B cells that stimulate their transition through the cell cycle. mAb to Bp35, like anti-immunoglobulin antibodies, functions principally to activate resting B cells to become competent to enter the G1 phase of the cell cycle. In contrast, mAb to Bp50, a 50-kDa polypeptide expressed on all B cells, functions to stimulate activated B cells to traverse the cell cycle. mAb to Bp35, like anti-immunoglobulin antibodies, activates tonsillar B cells and induces low levels of B-cell proliferation. In contrast, anti-Bp50 mAb alone neither activates B cells nor induces B cells to proliferate but, together with anti-Bp35 or anti-immunoglobulin, augments B-cell proliferation. In this respect the action of anti-Bp50 antibody resembles the activity of B-cell growth factor(s) (BCGF). As little as 0.05 microgram of anti-Bp50 per ml is needed to augment proliferation and, like BCGF, anti-Bp50 is effective even when added 12-24 hr after B cells are activated with anti-immunoglobulin or anti-Bp35. Without additional exogenous signals, anti-Bp35 and anti-Bp50 together induce strong proliferation of purified resting B cells. These results suggest that the Bp35 and Bp50 surface molecules function in the regulatory control of B-cell activation and progression through the cell cycle.
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000954:Antigens, Surface / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D002453:Cell Cycle; D002454:Cell Differentiation; D005434:Flow Cytometry; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology; D008213:Lymphocyte Activation; D008565:Membrane Proteins / Q000276:immunology; D008970:Molecular Weight; D011947:Receptors, Antigen, B-Cell / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D007075:Immunoglobulin M; D008565:Membrane Proteins; D011947:Receptors, Antigen, B-Cell