title: Human IgM anti-IgM cytotoxin for B lymphocytes.
abstract: B lymphocytes were shown previously to be killed at 5 degrees C by some autologous and allogeneic human sera. We show here that such cold cytotoxins are directed against immunoglobulins on the surface of B lymphocytes. The activity is partially removed by passing serum through IgG-coupled Sepharose and usually completely removed by passing serum through IgM-coupled Sepharose. Activity is regained from the columns by acid elution and IgM inhibits the cytotoxicity of these eluates. 125I-labeled eluates bind to IgG- and IgM-coupled Sepharose beads and binding is inhibited by IgM and to a lesser degree by IgG thus showing a primarily more avid binding to IgM as compared to IgG. Furthermore, the 125I-labeled cytotoxic eluates recognize the same determinant(s) on IgM and IgG. We suggest tht IgM anti-IgM antiimmunoglobulin may regulate immune reactivity by binding to B-lymphocyte surfaces.
mesh_terms: D000042:Absorption; D000888:Antibodies, Anti-Idiotypic; D001402:B-Lymphocytes / Q000276:immunology*; D001666:Binding Sites, Antibody; D003602:Cytotoxicity, Immunologic; D003603:Cytotoxins / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G; D007075:Immunoglobulin M / Q000276:immunology*; D012709:Serum Albumin / Q000276:immunology
chemical_list: D000888:Antibodies, Anti-Idiotypic; D003603:Cytotoxins; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D012709:Serum Albumin