title: Thymic T cell anergy in autoimmune nonobese diabetic mice is mediated by deficient T cell receptor regulation of the pathway of p21ras activation.
abstract: Thymic T cell anergy, as manifested by thymocyte proliferative unresponsiveness to antigens expressed in the thymic environment, is commonly believed to mediate the acquisition of immunological self-tolerance. However, we previously found that thymic T cell anergy may lead to the breakdown of tolerance and predispose to autoimmunity in nonobese diabetic (NOD) mice. Here, we show that NOD thymic T cell anergy, as revealed by proliferative unresponsiveness in vitro after stimulation through the T cell receptor (TCR), is associated with defective TCR-mediated signal transduction along the PKC/p21ras/p42mapk pathway of T cell activation. PKC activity is reduced in NOD thymocytes. Activation of p21ras is deficient in quiescent and stimulated NOD T cells, and this is correlated with a significant reduction in the tyrosine phosphorylation of p42mapk, a serine/threonine kinase active downstream of p21ras. Treatment of NOD T cells with a phorbol ester not only enhances their p21ras activity and p42mapk tyrosine phosphorylation but also restores their proliferative responsiveness. Since p42mapk activity is required for progression through to S phase of the cell cycle, our data suggest that reduced tyrosine phosphorylation of p42mapk in stimulated NOD T cells may abrogate its activity and elicit the proliferative unresponsiveness of these cells.
authors.affiliation: Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada.
authors.forename: M J
authors.initials: MJ
authors.lastname: Rapoport
authors.forename: A H
authors.initials: AH
authors.lastname: Lazarus
authors.forename: A
authors.initials: A
authors.lastname: Jaramillo
authors.forename: E
authors.initials: E
authors.lastname: Speck
authors.forename: T L
authors.initials: TL
authors.lastname: Delovitch
mesh_terms: D000818:Animals; D001327:Autoimmune Diseases / Q000276:immunology*; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D005260:Female; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D016688:Mice, Inbred NOD; D010766:Phosphorylation; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013950:Thymus Gland / Q000276:immunology*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D011948:Receptors, Antigen, T-Cell; D014443:Tyrosine; D016283:Proto-Oncogene Proteins p21(ras); D013755:Tetradecanoylphorbol Acetate