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.
Comparison of human B cell antigen receptor complexes: membrane-expressed forms of immunoglobulin (Ig)M, IgD, and IgG are associated with structurally related heterodimers.
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C J Van Noesel, G S Brouns, G M van Schijndel, R J Bende, D Y Mason, J Borst, R A van Lier; Comparison of human B cell antigen receptor complexes: membrane-expressed forms of immunoglobulin (Ig)M, IgD, and IgG are associated with structurally related heterodimers.. J Exp Med 1 June 1992; 175 (6): 1511–1519. doi: https://doi.org/10.1084/jem.175.6.1511
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