The cellular and molecular requirements for β‐cell damages in an immune‐mediated toxininduced insulin‐dependent diabetes mellitus have been studied in the model of multiple low‐dose streptozotocin‐induced diabetes in rats and mice. It was found that strain‐related susceptibility to diabetes induction correlated with a higher level of IL‐2, IFN‐γ, and TNF‐α production, whereas such differences were not observed when IL‐1 and NO production by macrophages were analyzed; elimination of immunoregulatory RT6⁺T cells that increases IFN‐γ production, enhances susceptibility to MLD‐STZ‐induced diabetes; mercury‐induced Th‐2 cells downregulated the disease; IFN‐γ‐mediated macrophage activation to produce proinflammatory cytokines rather than NO is an important event in early diabetogenic effects of invading macrophages; inhibition of IL‐1 activity downregulates diabetes induction; and generation of NO in β cells appears to be important for diabetogenic effects. Taken together, data indicate that MLD‐STZ diabetes is induced by Th‐1 lymphocytes that secrete soluble effector molecules that activate macrophages and promote destruction of β cells possibly by both nitric oxide and nonnitric oxide‐mediated mechanisms.

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that plays a pivotal role in several immunoinflammatory and autoimmune diseases. In this study we examined the role of MIF in the development of immunoinflammatory diabetes induced in susceptible strains of mice by multiple low doses of streptozotocin. We found that MIF protein was significantly elevated in islet cells during the development of diabetes, and that targeting MIF activity with either neutralizing antibody or the pharmacological inhibitor (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester, markedly reduced clinical and histopathological features of the disease, such as hyperglycemia and insulitis. Lymphocytes from mice treated with the MIF inhibitors exhibited reduction of both islet antigen-specific proliferative responses and adhesive cell-cell interactions. Neutralization of MIF also down-regulated the ex vivo secretion of the proinflammatory mediators, TNF-alpha, interferon-gamma, and nitric oxide, while augmenting that of the antiinflammatory cytokine, IL-10. This study provides the first in vivo evidence for a critical role for MIF in the immune-mediated beta-cell destruction in an animal model of human type 1 diabetes mellitus and identifies a new therapeutic strategy for the prevention and treatment of this disease in humans that is based on the selective inhibition of MIF activity.