ABSTRACT: We demonstrate diverse roles of interferonâgamma (IFN-γ) in the induction and regulation of immune-mediated inflammation using a transfer model of autoimmune diabetes. The diabetogenic CD4+BDC2.5 (BDC) T cell clone upon transfer into NOD.scid mice induced destruction of islets of Langerhans leading to diabetes. Administration of a neutralizing antibody to IFN-γ (H22) resulted in long term protection (LTP) from diabetes, with inflammation but persistence of a significant, albeit decreased numbers of β-cells. BDC T cells were a mixture of cells expressing high, intermediate and low levels of the T cell receptor. Clonotype-low BDC T cells were required for LTP. Furthermore, islet infiltrating leukocytes in the LTP mice contained Foxp3+CD4 T cells. Islet inflammation in both diabetic and LTP mice was characterized by heavy infiltration of macrophages. Gene expression profiles indicated that macrophages in diabetic mice were M1-type, while LTP mice contained M2-differentiated. The LTP was abolished if mice were treated with either an antibody depleting CD4 T cells, or a neutralizing antibody to CTLA-4, in this case, only at a late stage. Neutralization of IL-10, TGF-β, GITR or CD25 had no effect. Transfer of only clonotype-high expressing BDC T cells induced diabetes but in contrast, H22 antibodies did not inhibit diabetes. While clonotype high T cells induced diabetes even when IFN-γ was neutralized, paradoxically, there was reduced inflammation and no diabetes if host myeloid cells lacked IFN-γ receptor. Hence, using monoclonal CD4 T cells, IFN-γ can have a wide diversity of roles, depending on the setting of the immune process. Experiment Overall Design: Pancreatic islets were laser-capture microdissected from mice injected with diabetogenic T cells. One cohort of mice also received injections with anti-interfereon gamma monoclonal antibody, which protected those mice from developing diabetes. RNA prepared from islets was amplified and analyzed by Affymetrix GeneChips. Each GeneChip was prepared from RNA pooled from 5 mice at each timepoint. GeneChips were prepared from RNA extracted at different days following injection of T cells. The following days were assayed day 0 (i.e., untreated), day 3 (for diabetic and protected islets), day 4 (diabetic and protected), day 5 (only for protected, as diabetic islets were too edematous to dissect), day 8 (diabetic and protected).
