Islet transplantation for type 1 diabetic patients shows promising results with the use of nondiabetogenic immunosuppressive therapy. However, in addition to compromising the immune system of transplant recipients, long-term studies demonstrate that islet viability is impaired. Here, we demonstrate that, in the absence of immunosuppressive agents, monotherapy with clinical-grade human ␣1-antitrypsin (hAAT), the major serum serine-protease inhibitor, prolongs islet graft survival and normoglycemia in transplanted allogeneic diabetic mice, lasting until the development of anti-hAAT antibodies. Compared to untreated or albumin-controltreated graft recipients, which rejected islets at day 10, AATtreated mice displayed diminished cellular infiltrates and intact intragraft insulin production throughout treatment. Using peritoneal infiltration models, we demonstrate that AAT decreases allogeneic fibroblast-elicited natural-killer-cell influx by 89%, CD3-positive cell influx by 44%, and thioglycolate-elicited neutrophil emigration by 66%. ATT also extended islet viability in mice after streptozotocin-induced beta cell toxicity. In vitro, several islet responses to IL-1␤͞IFN␥ stimulation were examined. In the presence of AAT, islets displayed enhanced viability and inducible insulin secretion. Islets also released 36% less nitric oxide and 82% less macrophage inflammatory protein 1 ␣ and expressed 63% fewer surface MHC class II molecules. TNF␣ release from IL-1␤͞ IFN␥-stimulated islet cells was reduced by 99%, accompanied by an 8-fold increase in the accumulation of membrane TNF␣ on CD45-positive islet cells. In light of the established safety record and the nondiabetogenic potential of AAT, these data suggest that AAT may be beneficial as adjunctive therapy in patients undergoing islet transplantation.interleukin 1 ͉ nitric oxide ͉ TNF␣ I slet damage and an increased incidence of diabetes are associated with the use of immunosuppressive drugs in organ transplantation and present a major obstacle for clinically applicable human islet transplantation (1). Therefore, the advent of nondiabetogenic steroid-free, immunosuppressive treatment protocols, such as rapamycin-based protocols, have greatly facilitated human islet transplantation (reviewed in ref.2). However, although clinically effective, rapamycin-based protocols have been associated with an increased risk of hyperlipidemia and hypertension, limiting the applicability of islet transplantation to severe cases of diabetes type 1. Long-term follow-up studies reveal that the viability of engrafted islets is also compromised (3, 4).␣1-Antitrypsin (AAT), the major serum serine-protease inhibitor, inhibits the enzymatic activity of neutrophil elastase, cathepsin G, proteinase 3, thrombin, trypsin, and chymotrypsin (reviewed in ref. 5). AAT may facilitate the survival of islet transplants in engrafted patients, because the inhibitor prevents inflammatory cytokine production, blocks immune cell infiltration and function, inhibits complement activation, and delays the develop...

Acute exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can suppress adaptive immunity. In this study, pre-exposure of Leishmania major-infected mice to TCDD caused a dose-dependent and unexpected decrease in parasite burdens on day 20 after infection. In contrast, TCDD-mediated lymphoid atrophy, suppressed antibody levels, and enhanced interleukin-2 production were observed as expected. These results suggest that TCDD may enhance resistance to L. major in the face of immune suppression.