title: IgM binding protein expressed by activated B cells.
abstract: We have identified an IgM binding protein, a single chain polypeptide of Mr 60,000, that is expressed on the surface of B lymphocytes within 18 hr following their activation with phorbol myristate acetate. The IgM binding protein was also detected on fresh leukemic B cells from individuals with chronic lymphocytic leukemia, and the level of its expression was increased after phorbol myristate acetate activation. Resting and phorbol myristate acetate-activated T cells, monocytes, and polymorphonuclear leucocytes did not express detectable amounts of the IgM binding protein. The 60-kDa protein on activated human B cells could bind secreted IgM molecules of both mouse and human origin, as well as endogenous membrane-bound IgM molecules following their cross-linkage with anti-mu antibodies. The binding of soluble IgM molecules to the surface of activated B cells was also demonstrated by indirect immunofluorescence analysis.
mesh_terms: D001402:B-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D007075:Immunoglobulin M / Q000378:metabolism*; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D008970:Molecular Weight; D029584:Prostatic Secretory Proteins; D013601:T-Lymphocytes / Q000378:metabolism
chemical_list: D007075:Immunoglobulin M; D008222:Lymphokines; D029584:Prostatic Secretory Proteins; C043076:beta-microseminoprotein; C013059:immunoglobulin-binding factors