title: Clonal analysis of human T cell activation by the Mycoplasma arthritidis mitogen (MAS).
abstract: Mycoplasma arthritidis produces an as yet undefined soluble molecule (MAS) that has a potent mitogenic effect on T cells of several species. We have used cloned human cytotoxic and proliferative T lymphocytes to dissect the molecular mechanism of T cell activation by this mitogen. Reactivity to MAS is clonally expressed among T cell receptor (TcR) alpha/beta chain-expressing T cell clones of CD4+ or CD8+ phenotype, as well as CD4-8- TcR alpha/beta chain-negative T lymphocyte clones expressing the CD3-associated TcR gamma chain. MAS is able to induce cytotoxicity and/or proliferation in these T cell clones. For triggering of these T cells, regardless of their phenotype of specificity, the presence of autologous, allogeneic or xenogeneic major histocompatibility complex (MHC) class II molecules on accessory cells or target cells is necessary. However, T cells do not immunologically recognize MAS on class II molecules, since a direct action of MAS on the T cells themselves can be demonstrated. Triggering of T cells by MAS can be blocked by monoclonal antibodies against CD2, CD3 and the TcR alpha/beta chain dimer. We discuss as a possible explanation that MAS is a functionally bivalent molecule cross-linking TcR and MHC class II molecules. Thus, the mechanism of T cell activation by MAS has striking similarities to the mechanisms by which Staphylococcal enterotoxins activate T cells. It is intriguing that a similar mitogenic principle has been developed by two evolutionary distinct pathogenic microorganisms.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Ulm, FRG.
authors.forename: M
authors.initials: M
authors.lastname: Matthes
authors.forename: H
authors.initials: H
authors.lastname: Schrezenmeier
authors.forename: J
authors.initials: J
authors.lastname: Homfeld
authors.forename: S
authors.initials: S
authors.lastname: Fleischer
authors.forename: B
authors.initials: B
authors.lastname: Malissen
authors.forename: H
authors.initials: H
authors.lastname: Kirchner
authors.forename: B
authors.initials: B
authors.lastname: Fleischer
mesh_terms: D000937:Antigen-Antibody Reactions; D000942:Antigens, Bacterial / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology; D002999:Clone Cells; D003602:Cytotoxicity, Immunologic; D006681:HLA-D Antigens / Q000276:immunology; D006801:Humans; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D009174:Mycoplasma / Q000276:immunology*; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D013045:Species Specificity; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial; D000945:Antigens, Differentiation, T-Lymphocyte; D006681:HLA-D Antigens; D011948:Receptors, Antigen, T-Cell