title: In vivo apoptosis of diabetogenic T cells in NOD mice by IFN-gamma/TNF-alpha.
abstract: Immunization with mycobacterial preparation such as Bacille Calmette-Guerin (BCG) or complete Freund's adjuvant (CFA) prevents the onset and recurrence of type 1 diabetes in non-obese diabetic (NOD) mice. In this study, we explored the mechanism underlying the down-regulation of diabetogenic T cells by BCG treatment. We found that the potential of splenocytes from BCG-immunized diabetic NOD mice to adoptively transfer diabetes was significantly impaired. BCG immunization sequentially induced the production of TNF-alpha, IFN-gamma and IL-4 by splenocytes, increased the expression of Fas(high) (Apo-1/CD95), Fas ligand (FasL, CD95L) and TNF receptor (TNFR) on T cells leading to T cell apoptosis. The primary role of IFN-gamma and TNF-alpha in BCG-immunotherapy was demonstrated by (i) reversing the immune regulatory effect of BCG by in vivo treatment with neutralizing anti-cytokine antibodies, (ii) inducing effect similar to BCG by treatment with these cytokines. We show that Fas and TNF are two pathways in BCG-induced apoptosis of diabetogenic T cells, since in vitro blocking FasL or TNFR1 with antibody reduced T cell apoptosis and increased T cell proliferative response. In addition, TNF-alpha and agonistic anti-Fas antibody had a synergistic effect on the in vitro apoptosis of diabetogenic T cells. Our results suggest that BCG down-regulates destructive autoimmunity by TNF-alpha/IFN-gamma-induced apoptosis of diabetogenic T cells through both Fas and TNF pathways. These studies provide a novel mechanism for blocking disease recurrence and immune modulating effect of BCG immunization in type 1 diabetes.
authors.affiliation: Department of Microbiology and Immunology, University of Western Ontario, Canada.
authors.forename: Hui-Yu
authors.initials: HY
authors.lastname: Qin
authors.forename: Pratibha
authors.initials: P
authors.lastname: Chaturvedi
authors.forename: Bhagirath
authors.initials: B
authors.lastname: Singh
mesh_terms: D000818:Animals; D017209:Apoptosis; D015551:Autoimmunity; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology* / Q000628:therapy; D053222:Fas Ligand Protein; D007114:Immunization; D016233:Immunotherapy, Active; D007371:Interferon-gamma / Q000494:pharmacology / Q000502:physiology*; D015847:Interleukin-4 / Q000494:pharmacology / Q000502:physiology; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D016688:Mice, Inbred NOD; D009163:Mycobacterium bovis / Q000276:immunology*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism; D055502:Secondary Prevention; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology / Q000502:physiology*; D019014:fas Receptor / Q000378:metabolism
chemical_list: D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D015847:Interleukin-4; D007371:Interferon-gamma