Molecular components of the B-cell antigen receptor complex of the IgM class.
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.
Hombach
J
J
Max-Planck-Institut für Immunbiologie, Freiburg, FRG.
Tsubata
T
T
Leclercq
L
L
Stappert
H
H
Reth
M
M
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D002462:Cell Membrane / Q000276:immunology; D004220:Disulfides / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D007075:Immunoglobulin M / Q000235:genetics / Q000378:metabolism*; D008223:Lymphoma / Q000276:immunology; D046911:Macromolecular Substances; D051379:Mice; D008970:Molecular Weight; D009101:Multiple Myeloma; D011947:Receptors, Antigen, B-Cell / Q000235:genetics / Q000378:metabolism*; D011961:Receptors, Fc / Q000235:genetics / Q000378:metabolism*; D015183:Restriction Mapping; D014162:Transfection; D014407:Tumor Cells, Cultured
D004220:Disulfides; D007075:Immunoglobulin M; D046911:Macromolecular Substances; D011947:Receptors, Antigen, B-Cell; D011961:Receptors, Fc; C035311:immunoglobulin M receptor