Comparison of human B cell antigen receptor complexes: membrane-expressed forms of immunoglobulin (Ig)M, IgD, and IgG are associated with structurally related heterodimers.
We have recently reported that on human B lymphocytes, membrane IgM (mIgM) associates with a heterodimer of 47- and 37-kD polypeptides, the 47-kD subunit being encoded by the mb-1 gene. We show here that expression of mb-1, both at the mRNA and the protein level, is not restricted to IgM+ B cells but can also be found in IgM- pre-B cells and mIgM-IgG+ B cells. Membrane forms of IgD and IgG, isolated from freshly isolated human B cells and B cell lines, are expressed together with heterodimeric protein structures biochemically similar to the mIgM-associated polypeptides, and these were shown to comprise the products of the mb-1 and B29 genes, or homologous genes. Finally, all three classes of antigen receptors are linked to protein kinases, capable of phosphorylating the Ig-associated heterodimers. Our findings provide insight in the structural organization of the different antigen receptors on human B cells and have implications for their function.
Van Noesel
C J
CJ
Department of Clinical Viro-Immunology, The Netherlands Red Cross Blood Transfusion Service, Amsterdam.
Brouns
G S
GS
van Schijndel
G M
GM
Bende
R J
RJ
Mason
D Y
DY
Borst
J
J
van Lier
R A
RA
D000911:Antibodies, Monoclonal; D001402:B-Lymphocytes / Q000276:immunology*; D015152:Blotting, Northern; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology; D005455:Fluorescent Antibody Technique; D005803:Genes, Immunoglobulin; D006801:Humans; D007072:Immunoglobulin D / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D007074:Immunoglobulin G / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D007075:Immunoglobulin M / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D007146:Immunoglobulin lambda-Chains / Q000032:analysis; D007148:Immunoglobulin mu-Chains / Q000032:analysis; D046911:Macromolecular Substances; D008970:Molecular Weight; D014066:Palatine Tonsil / Q000276:immunology; D010766:Phosphorylation; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000032:analysis / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D007072:Immunoglobulin D; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007146:Immunoglobulin lambda-Chains; D007148:Immunoglobulin mu-Chains; D046911:Macromolecular Substances; D012333:RNA, Messenger; D011947:Receptors, Antigen, B-Cell; D012313:RNA