Islet T Cells Secreting IFN-γ in NOD Mouse Diabetes: Arrest by p277 Peptide Treatment

Abstract

Non-obese diabetic (NOD) mice spontaneously develop insulin-dependent (type 1) diabetes mellitus (IDDM) caused by T cells which destroy the insulin-producing islet β-cells. Since cytokines are involved in this auto-immune β-cell damage, we used an ELISPOT assay to enumerate the islet-associated T cells that secreted interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α) or interleukin-4 (IL-4). We used mitogenic anti-CD3 antibody to activate all the T cells capable of responding, irrespective of their antigen specificity. We found that NOD females, more susceptible than males to IDDM, accumulated islet IFN-γ producers more rapidly with age than did the males. Acceleration of male IDDM by cyclophosphamide led to a marked increase in IFN-γ secreting islet T cells. In contrast, a decrease in IFN-γ-producing islet T cells was associated with arrest of IDDM by administration of peptide p277 of the 60kDa heat-shock protein (hsp60) to 12-week-old female NOD mice. The p277-treated mice later manifested a greater number of islets and fewer leukocytes per islet than did the mice treated with a bacterial hsp60 peptide. Thus, the development of diabetes could be correlated with the accumulation in the islets of T cells producing IFN-γ, and destructive insulitis could be downregulated by the administration of a single peptide.