Immunopathology and Infectious Disease Induction of Active Tolerance and Involvement of CD 1 d-Restricted Natural Killer T Cells in Anti-CD 3 F ( ab ) 2 Treatment-Reversed New-Onset Diabetes in Nonobese Diabetic Mice

The application of anti-CD3 F(ab )2 monoclonal antibodies has recently been expanded to treat established autoimmune diseases, including type 1 diabetes. However, the mechanism underlying their effect remains largely unclear. We report that short-phase administration of anti-CD3 F(ab )2 antibodies efficiently allowed 80% of new-onset, nonobese diabetic (NOD) mice to significantly regain both normoglycemia and pancreatic cell-specific autoantigen (ie, glutamic acid decarboxylase and insulin) tolerance, with both effects lasting more than 40 weeks. The responsible mechanism appears to involve the induction and maintenance of a population of immunoregulatory CD1d-restricted natural killer T (NKT) cells, which were marked by an enhanced Th2 response and secretion of elevated levels of interleukin-10. In vivo neutralization of interleukin-4 and/or interleukin-10 bioactivity abrogated this anti-CD3-mediated effect. Importantly, when the cotransfer of NKT cells from the livers of anti-CD3-treated mice and splenocytes from untreated, acutely diabetic NOD mice was performed in NOD-severe combined immunodeficient mice, the NKT cells were sufficient to either delay or prevent the onset of diabetes compared with controls where only splenocytes were introduced. These data suggest that CD1d-restricted NKT cells may play a critical role in anti-CD3 antibody-induced diabetes remission and the restoration of immune tolerance. (Am J Pathol 2008, 172:972–979; DOI: 10.2353/ajpath.2008.070159) Type 1 diabetes is an autoimmune disease characterized by immunological destruction of insulin-producing pancreatic cells and subsequent hyperglycemia. The development of type 1 diabetes is influenced by multiple genetic and environmental factors, most of which remain unknown. The nonobese diabetic (NOD) mouse strain spontaneously develops a disease similar to human type 1 diabetes as a consequence of the loss of basic tolerogenic processes designed to control self/nonself discrimination. Many studies have demonstrated that defects of several regulatory lymphocytes contribute to the pathogenesis of type 1 diabetes, including CD4 regulatory T cells (Tregs) and natural killer T (NKT) cells coexpressing T and NK cell receptors. The number and function of these cells are impaired in NOD mice and individuals at risk for type 1 diabetes. Increasing the number by adoptive transfer, or by augmenting function of these regulatory cells by T cell receptor engagement, has potential for the prevention and treatment of diabetes. Manipulation of CD4 Tregs or NKT cells has been shown to be involved in antigen-induced tolerance to self islets. Anti-CD3 monoclonal antibody (mAb) (OKT3) is commonly considered as a category of immunomodulatory agents for silencing acute allograft rejection. Its therapeutic role in autoimmune diabetes has been recently reported that the treatment of new-established diabetes with anti-CD3 F(ab )2 resulted in durable disease remission in animals or reduced usage of insulin in humans involving Th2 deviation. A population of CD4 CD25 Tregs has been proposed to be implicated in this effect. However, whether other immunoregulatory path-