Molecular components of the B-cell antigen receptor complex of the IgM class

Nature. 1990 Feb 22;343(6260):760-2. doi: 10.1038/343760a0.


The antigen receptors on mature B lymphocytes are membrane-bound immunoglobulins of the IgM and IgD classes whose cross-linking by polyvalent antigens results in B-cell proliferation and differentiation. How these membrane-bound immunoglobulin chains, which lack a cytoplasmic tail, generate a cell activation signal is not at present known. We now show that the IgM molecule is non-covalently associated in the membrane of B cells with two proteins of relative molecular mass 34,000 (Mr 34 K; IgM-alpha) and 39 K (Ig-beta) which form a disulphide-linked heterodimer. Surface expression of IgM seems to require the formation of an appropriate complex between IgM and the heterodimer. A transfection experiment indicates that IgM-alpha is the product of mb-1, a B-cell specific gene encoding a transmembrane protein with sequence homology to proteins of the T-cell antigen receptor-CD3 complex.

MeSH terms

  • Animals
  • B-Lymphocytes / immunology*
  • Cell Membrane / immunology
  • Disulfides / metabolism
  • Electrophoresis, Gel, Two-Dimensional
  • Humans
  • Immunoglobulin M / genetics
  • Immunoglobulin M / metabolism*
  • Lymphoma / immunology
  • Macromolecular Substances
  • Mice
  • Molecular Weight
  • Multiple Myeloma
  • Receptors, Antigen, B-Cell / genetics
  • Receptors, Antigen, B-Cell / metabolism*
  • Receptors, Fc / genetics
  • Receptors, Fc / metabolism*
  • Restriction Mapping
  • Transfection
  • Tumor Cells, Cultured


  • Disulfides
  • Immunoglobulin M
  • Macromolecular Substances
  • Receptors, Antigen, B-Cell
  • Receptors, Fc
  • immunoglobulin M receptor