title: Expression of a 33-kDa antigen Tm 1 on lymphocyte surface after modulation of cell surface antigens by IgM monoclonal antibody.
abstract: The mAb Tm 1 was obtained from a fusion of SP2/O tumor cells with spleen cells from CF1 mouse immunized with T cells modulated by an IgM anti-CD3 mAb.mAb Tm 1 reacted with IgM anti-CD3 modulated T cells (66.6%) but not with unmodulated T cells (4.4%). Tm 1 was not expressed on T cells modulated with either IgG2a or IgG1 anti-CD3 mAb. Immunoprecipitation from 125I-labeled CD3-modulated T cells showed that Tm 1 Ag is a single polypeptide of 33 kDa under reducing and nonreducing conditions. Kinetic studies revealed that Tm 1 was detectable on T cells 10 min after incubation and maximally expressed after 4 h of incubation with IgM anti-CD3 mAb. CD3 expression was markedly modulated by this anti-CD3 mAb after the same period of incubation. Studies with cycloheximide revealed that Tm 1 expression on T cells does not require new protein synthesis. Tm 1 expression persisted long after CD3-reexpression 24 h later. Tm 1 was present on a small fraction of circulating T cells, B cells, and monocytes and absent from granulocytes, platelets, E, and thymocytes. Tm 1 was not expressed on T cells after various activation stimuli but was expressed on B cells upon activation. Additional studies indicate that IgM mAb against other T cell differentiation Ag and IgM mAb against B cell Ag also lead to the expression of Tm 1 on these cells. Thus, modulation of surface Ag by IgM mAb externalizes this cytoplasmic Ag. However, one exception has been noted. Purified mAb Tm 1 was not mitogenic and was unable to block either the T cell proliferation induced by 12-O-tetradecanoyl phorbol-13-acetate plus anti-CD3 mAb and other T cell stimuli, or the B cell proliferation induced by B cell mitogens. The role of Tm 1 on lymphocyte function remains to be determined.
mesh_terms: D000818:Animals; D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000943:Antigens, Differentiation / Q000032:analysis* / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology; D000951:Antigens, Neoplasm / Q000032:analysis; D017252:CD3 Complex; D003513:Cycloheximide / Q000494:pharmacology; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology*; D007942:Leukemia, Experimental / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D013601:T-Lymphocytes / Q000276:immunology*; D014407:Tumor Cells, Cultured / Q000276:immunology
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation; D000945:Antigens, Differentiation, T-Lymphocyte; D000951:Antigens, Neoplasm; D017252:CD3 Complex; D007074:Immunoglobulin G; D007075:Immunoglobulin M; C044203:anti-IgM; D003513:Cycloheximide