Dietary protection against diabetes in NOD mice: lack of a major change in the immune system.

Pregestimil, a hypoallergenic infant formula in which casein hydrolysate replaces protein, protects NOD mice against diabetes, a T-cell-mediated autoimmune disease. Female and cyclosphosphamide (Cy)-treated male NOD mice were used to assess whether a modification of cellular immune mechanisms occurred when animals were fed Pregestimil from weaning to 110 days of life. Insulitis, sialitis and thyroiditis were observed, and the splenic T-cell proliferative response was measured. The ability of splenic T-cells of NOD mice in the Pregestimil group to transfer diabetes adoptively to young irradiated male NOD mice was also assessed. Pregestimil protected female NOD mice against spontaneous diabetes and male NOD mice against acute Cy-induced diabetes. Addition of bovine serum albumin (10%) to the diet did not alter the preventive effect. The Pregestimil diet also lessened insulitis severity in Cy-treated males, though not in females. Sialitis and thyroiditis, observed mainly in females, were not modified by the diets. The TCR-mediated proliferative response of splenocytes tended to increase specifically in Pregestimil-fed and Cy-treated males. Sensitivity to IL-2 was improved. In females, the TCR-mediated proliferative response and the ability of T cells to transfer diabetes adoptively were unchanged. It is concluded that the protective effect of Pregestimil against diabetes in NOD mice cannot be explained by major changes in peripheral immune response.