The Role of Type I Interferon Subtypes and Interferon-Gamma in Type I Interferon Diabetes Inhibitory Activity in the NOD Mouse.

As in bacterial infections and endotoxin shock, type I interferons (IFNs) also have complex and often opposing effects in various models of autoimmune disease. We have shown that type I IFN paradoxically inhibits autoimmune diabetes in the nonobese diabetic mouse (NOD) and biobreeding (BB) rat. We hypothesize that type I IFN activity differs by IFN subtype and interaction with IFN-gamma. We examined the structure-function relationship of the type I IFN molecule and the mechanism of its diabetes-sparing activity in the NOD mouse. While both recombinant human IFN-alpha A/D (bgl 11) (rHuIFN-alphaA/D) and ovine IFN-tauImod (ovIFN-tau) potently inhibited the development of diabetes (P < 0.01), neither recombinant human IFN-alpha B/D (rHuIFN-alphaB/D) nor recombinant human IFN-alpha consensus (CIFN) were efficacious. The activity of IFN subtypes correlate with their NH3-terminal amino acid sequences. All type I IFN save CIFN, which has no diabetes-sparing activity, inhibited the accessory cell function. IFN-tau administration decreased the expression of Fas and ICAM on total cells, class II MHC expression on B cells, and CD40L expression on T cells by 39%, 45%, 45%, and 60%, respectively. In addition, IFN-tau inhibited the development of diabetes in the NOD.IL4(null) but not the NOD.IFN-gamma(null) mice, suggesting a coordinated interaction between type I and type II IFNs to suppress diabetes development. Thus, the amino terminal portion of the type I IFN molecule influences its ability to inhibit the development of autoimmune diabetes in NOD mice. These data also support the contention that IFN-gamma may have a role in mediating the diabetes-sparing effect of high-dose type I IFNs by the inhibition of the IFN-gamma-inducible immune modulators, class II MHC, Fas, ICAM, and CD40L.

Interferon-tau inhibits the development of diabetes in NOD mice.

Interferon-alpha (IFN-alpha) inhibits the development of diabetes in animal models of autoimmune diabetes. However, the mechanism of the action is not fully understood and drug toxicity could limit its potential clinical utility. Interferon-tau (IFN-tau) is another type 1 interferon, which has less toxicity but may have different biologic activity than IFN-alpha. This study explores the effect of IFN-tau on the diabetic process in non-obese diabetic (NOD) mice. IFN-tau by intraperitoneal, subcutaneous, or oral routes of administration decreased the development of spontaneous diabetes in NOD mice. Islet inflammation was decreased 50%. IFN-tau administration to recipient mice prevented the development of passively transferred and cyclophosphamide accelerated diabetes. IFN-tau treatment also decreased anti-islet effector activity of NOD splenic cells. Immunoregulatory activity of splenic cells was augmented by IFN-tau administration as was the number of splenic CD25+CD4+ cells. Concanavalin A (Con A)-induced release of IFN-gamma was decreased in spleen cells from IFN-tau treated mice. In conclusion, IFN-tau inhibits spontaneous autoimmune diabetes and passively transferred diabetes in the NOD mouse. This diabetes sparing activity may be due to an induction of regulatory cells, possibly CD25+CD4+ T cells, which in turn inhibit anti-islet effector cell activity and the development of insulitis and diabetes. Due to the lower drug toxicity, IFN-tau could be a better drug candidate than IFN-alpha for experimental clinical trials.

Gamma interferon paradoxically inhibits the development of diabetes in the NOD mouse.

Gamma interferon (IFN-gamma) has been thought to play an important role in the pathogenesis of diabetes. This report determines if rIFN-gamma administration to NOD mice paradoxically inhibits the development of diabetes. Injections of recombinant rIFN-gamma of 5 x 10(3), 20 x 10(3), and 100 x 10(3) units, dose dependently inhibited the development of diabetes. The maximal rIFN-gamma dose decreased the incidence of diabetes from 74% in control animals to 42%. 100x10(3) unit rIFN-gamma dose significantly decreased insulitis score, and increased islet number. The development of diabetes in irradiated NOD mice was slower in animals injected with spleen cells from rIFN-gamma treated than from saline treated NOD mice suggesting that rIFN-gamma decreases anti-islet effector cell activity. The susceptibility to apoptosis was increased in splenic cells of rIFN-gamma treated mice. The expressions of the co-stimulatory molecules B7-2 and ICAM-1 were significantly increased in spleen cells of rIFN-gamma treated mice while the expression of MHC class I was decreased. In vitro studies demonstrated that NOD mouse mononuclear spleen cells preincubated with rIFN-gamma and subsequently cocultured with responder cells, potently inhibited responder T-cell proliferative responses. rIFN-gamma administration decreased IL-12 and IL-2 mRNA expression in spleen cells while increasing IL-1 expression. In conclusion, rIFN-gamma inhibits the diabetic process in NOD mice by decreasing anti-islet effector activity and in turn decreasing insulitis and islet destruction. The suppression of Th1 cell related cytokines and/or augmentation of the macrophage cytokine IL-1 may play a role in the diabetes sparing effect of rIFN-gamma.