title: A new epitope of the T200 molecule family defined by the 3A35 monoclonal antibody and expressed by macrophages and activated T lymphocytes.
abstract: A monoclonal antibody (mAb), 3A35, produced against mouse macrophages (M phi) was found to react against certain activated T cells. This mAb, a rat IgM, resulted from a cell fusion between a mouse plasmacytoma and rat lymphocytes immunized against mouse M phi. It bound more avidly to activated than to resident M phi. It did not react against B cells and resting T lymphocytes but recognized certain dividing T cells like EL4 lymphoma, concanavalin A-activated and interleukin 2-expanded spleen cells, and helper T cell hybridomas. By contrast, other T lymphocyte-derived cell lines such as YAC-1 and CTLL2 were unreactive. No clear relationship was found between the binding of 3A35 to cells and the expression of L3T4 and Lyt-2 antigens. The specific stimulation of T cell clones with antigen rapidly induced a strong reactivity with 3A35 mAb which declined thereafter to a low (helper clones) or non-reactivity (cytotoxic clones) after 10 days of culture. Immunoprecipitation experiments, performed with M phi derived from bone marrow cell cultures, surface iodinated with 125I or metabolically labeled with [35S]methionine, showed that 3A35 bound to a 200-kDa molecule, shifting to 175 kDa under reducing conditions. In peritoneal M phi activated in vivo, in addition to the 175-kDa band, new bands migrating at 140, 120 and 85 kDa were identified by 3A35 and could be absorbed on a commercial anti-T200 mAb bound to Sepharose beads. After strengthening the cell binding of 3A35 to EL4 lymphoma cells by a cross-linking agent, only a 85-kDa molecule was immunoprecipitated. Thus, 3A35 identifies a new epitope of the T200 molecule family which is expressed on M phi and activated T cells.
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D000939:Epitopes; D005434:Flow Cytometry; D006649:Histocompatibility Antigens / Q000276:immunology*; D007152:Immunologic Capping; D017493:Leukocyte Common Antigens; D008213:Lymphocyte Activation; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008970:Molecular Weight; D013601:T-Lymphocytes / Q000145:classification / Q000166:cytology / Q000276:immunology*
chemical_list: D000954:Antigens, Surface; D000939:Epitopes; D006649:Histocompatibility Antigens; D017493:Leukocyte Common Antigens