CD28 co-stimulation restores T cell responsiveness in NOD mice by overcoming deficiencies in Rac-1/p38 mitogen-activated protein kinase signaling and IL-2 and IL-4 gene transcription.
Previously, we reported that T cell hyporesponsiveness induced by TCR ligation is causal to autoimmune diabetes in NOD mice. Neonatal CD28 co-stimulation reverses T cell hyporesponsiveness and protects NOD mice from diabetes by an IL-4-mediated mechanism, indicating that a deficiency in TCR signaling may be overcome by CD28/B7-2 co-stimulation in NOD T cells. To investigate which co-stimulation-induced signaling events mediate this protection, we analyzed the activity of Ras, Rac-1, mitogen-activated protein kinases (MAPK) and several transcription factors in TCR-activated NOD T cells in the presence or absence of CD28 co-stimulation. We show that CD28 co-stimulation restores normal TCR-induced activation of Rac-1 and p38 MAPK in NOD T cells. Deficiencies in TCR-induced nuclear expression of activating protein (AP)-1 binding proteins as well as activation of AP-1 and NF-AT in the IL-2 and IL-4 P1 promoters are also corrected by CD28 co-stimulation. Thus, CD28 co-stimulation reverses NOD T cell hyporesponsiveness by restoring TCR signaling leading to the activation of AP-1 and NF-AT during IL-2 and IL-4 gene transcription. Our findings provide additional evidence that CD28 co-stimulation amplifies signals delivered by the TCR and further explain the mechanism by which CD28 co-stimulation may protect against autoimmune diabetes.
Zhang
J
J
Autoimmunity/Diabetes Group, The John P. Robarts Research Institute, London, Ontario N6G 2V4, Canada.
Salojin
K V
KV
Delovitch
T L
TL
D021581:Active Transport, Cell Nucleus; D000818:Animals; D001327:Autoimmune Diseases / Q000235:genetics / Q000276:immunology* / Q000517:prevention & control; D018106:CD28 Antigens / Q000276:immunology*; D017635:Clonal Anergy; D004247:DNA / Q000378:metabolism; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics / Q000276:immunology* / Q000517:prevention & control; D005260:Female; D007376:Interleukin-2 / Q000096:biosynthesis / Q000235:genetics*; D015847:Interleukin-4 / Q000096:biosynthesis / Q000235:genetics*; D008213:Lymphocyte Activation / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000235:genetics / Q000502:physiology*; D051379:Mice; D016688:Mice, Inbred NOD; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000502:physiology; D013047:Specific Pathogen-Free Organisms; D013601:T-Lymphocytes / Q000276:immunology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein / Q000172:deficiency* / Q000235:genetics / Q000502:physiology
D018106:CD28 Antigens; D007376:Interleukin-2; D016328:NF-kappa B; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D015847:Interleukin-4; D004247:DNA; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D016283:Proto-Oncogene Proteins p21(ras); D020830:rac1 GTP-Binding Protein