title: Defective thymic T cell activation by concanavalin A and anti-CD3 in autoimmune nonobese diabetic mice. Evidence for thymic T cell anergy that correlates with the onset of insulitis.
abstract: In nonobese diabetic (NOD) mice, T cells play a major role in mediating autoimmunity against pancreatic islet beta-cells. We and others previously reported that age-related alterations in the thymic and peripheral T cell repertoire and function occur in prediabetic NOD mice. To study the mechanism responsible for these T cell alterations, we examined whether a defect exists in the thymus of NOD mice at the level of TCR-mediated signaling after activation by Con A and anti-CD3. We found that thymocytes from NOD mice respond weakly to Con A- and anti-CD3-induced proliferation, compared with thymocytes from control BALB/c, BALB.B, (BALB.B x BALB.K)F1, C57BL/6, and nonobese non-diabetic mice. This defect correlates with the onset of insulitis, because it can be detected at 7 to 8 weeks of age, whereas younger mice displayed a normal T cell responsiveness. Thymic T cells from (NOD x BALB/c)F1 mice, which are insulitis- and diabetes-free, exhibit an intermediate stage of unresponsiveness. This T cell defect is not due to a difference in the level of CD3 and IL-2R expression by NOD and BALB/c thymocytes, and both NOD CD4+ CD8- and CD4- CD8+ mature thymic T cells respond poorly to Con A. BALB/c but not NOD thymic T cells respond to Con A in the presence of either BALB/c or NOD thymic APC, suggesting that the thymic T cell defect in NOD mice is intrinsic to NOD thymic T cells and is not due to an inability of NOD APC to provide a costimulatory signal. The defect can be partially reversed by the addition of rIL-2 to NOD thymocytes. To determine whether a defect in signal transduction mediates this NOD thymic T cell unresponsiveness, we tested whether these cells elevate their intracellular free Ca2+ ion concentration in response to Con A. An equivalent Con A-induced increase in Ca2+ ion concentration in both NOD and BALB/c thymocytes was observed, suggesting a normal coupling between the CD3 complex and phospholipase C in NOD thymocytes. In contrast to their low proliferative response to Con A or anti-CD3, NOD thymocytes respond normally (i.e., as do BALB/c thymocytes) to the combinations of PMA plus the Ca2+ ionophore ionomycin and PMA plus Con A but weakly to Con A plus ionomycin. Our data suggest that the age-related NOD thymocyte unresponsiveness to Con A and anti-CD3 results from a defect in the signaling pathway of T cell activation that occurs upstream of protein kinase C activation.
authors.affiliation: Banting and Best Department of Medical Research, University of Toronto, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Zipris
authors.forename: A H
authors.initials: AH
authors.lastname: Lazarus
authors.forename: A R
authors.initials: AR
authors.lastname: Crow
authors.forename: M
authors.initials: M
authors.lastname: Hadzija
authors.forename: T L
authors.initials: TL
authors.lastname: Delovitch
mesh_terms: D000367:Age Factors; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D015703:Antigens, CD / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis / Q000276:immunology*; D017252:CD3 Complex; D002118:Calcium / Q000378:metabolism; D003208:Concanavalin A / Q000494:pharmacology*; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D007376:Interleukin-2 / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D011948:Receptors, Antigen, T-Cell / Q000032:analysis / Q000276:immunology*; D011994:Recombinant Proteins / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell; D011994:Recombinant Proteins; D003208:Concanavalin A; D015759:Ionomycin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium