title: MHC class II molecules regulate growth in human T cells.
abstract: MHC-class-II-positive T cells are found in tissues involved in autoimmune disorders. Stimulation of class II molecules by monoclonal antibodies (mAbs) or bacterial superantigens induces protein tyrosine phosphorylation through activation of protein tyrosine kinases in T cells, and class II signals modulate several T cell responses. Here, we studied further the role of class II molecules in the regulation of T cell growth. Costimulation of class II molecules by immobilized HLA-DR mAb significantly enhanced interleukin (IL)-2-supported T cell growth of the majority of CD4+, CD45RAlow, ROhigh T cell lines tested. Only one of three CD4+, CD45RAhigh, ROhigh T cells responded to class II costimulation. There was no correlation between T cell responsiveness to class II and the cytokine production profile of the T cell in question. Thus, T cell lines producing interferon (IFN)-gamma but not IL-4 (TH1-like) as well as T cells producing both cytokines (THO-like) responded to class II mAb. The costimulatory effect was not restricted to IL-2-driven T cell growth, since TCR/CD3-induced T cell activation was also enhanced by HLA-DR mAb. Moreover, class II costimulation potentiated CD28-mAb-induced T cell sensitivity to protein kinase C activation by phorbol 12-myristate 13-acetate. In conclusion, class II costimulation enhances T cell activation through the TCR/CD3 and IL-2 pathways and interacts with CD28 accessory signals to up-regulate growth of allospecific T cell lines.
authors.affiliation: Department of Clinical Immunology, State University Hospital (Rigshospitalet), Copenhagen, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Nielsen
authors.forename: N
authors.initials: N
authors.lastname: Odum
authors.forename: K
authors.initials: K
authors.lastname: Bendtzen
authors.forename: L P
authors.initials: LP
authors.lastname: Ryder
authors.forename: B K
authors.initials: BK
authors.lastname: Jakobsen
authors.forename: A
authors.initials: A
authors.lastname: Svejgaard
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D018106:CD28 Antigens / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D006681:HLA-D Antigens / Q000276:immunology*; D006682:HLA-DP Antigens / Q000276:immunology; D006684:HLA-DR Antigens / Q000276:immunology; D006801:Humans; D007376:Interleukin-2 / Q000502:physiology; D017493:Leukocyte Common Antigens / Q000276:immunology; D008213:Lymphocyte Activation; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D018106:CD28 Antigens; D006681:HLA-D Antigens; D006682:HLA-DP Antigens; D006684:HLA-DR Antigens; D007376:Interleukin-2; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D017493:Leukocyte Common Antigens; D013755:Tetradecanoylphorbol Acetate