Activation of human B cells mediated through two distinct cell surface differentiation antigens, Bp35 and Bp50

Proc Natl Acad Sci U S A. 1986 Jun;83(12):4494-8. doi: 10.1073/pnas.83.12.4494.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antibodies, Monoclonal / immunology
  • Antigens, Surface / immunology*
  • B-Lymphocytes / immunology*
  • Cell Cycle
  • Cell Differentiation
  • Flow Cytometry
  • Humans
  • Immunoglobulin M / immunology
  • Lymphocyte Activation
  • Membrane Proteins / immunology
  • Molecular Weight
  • Receptors, Antigen, B-Cell / immunology


  • Antibodies, Monoclonal
  • Antigens, Surface
  • Immunoglobulin M
  • Membrane Proteins
  • Receptors, Antigen, B-Cell