Abstract
Background. Immunotherapy with Complete Freund's adjuvant (CFA) is effective in ameliorating autoimmunity in diabetic nonobese diabetic (NOD) mice. We investigated whether CFA treatment up-regulates CD4(+)CD25(+)Foxp3(+) regulatory T cells and increases transforming growth factor (TGF)-beta 1 production in diabetic NOD mice.
Methods. New-onset diabetic NOD mice were treated with CFA and exendin-4, a potent analog of glucagon-like peptide-1. Reversal of diabetes was determined by monitoring blood glucose level. Ameliorating autoimmunity through immunoregulation was assessed by adoptive transfer. Regulatory T cells in the peripheral blood, spleen, thymus, and pancreatic nodes were measured. TGF-beta 1 in plasma and the insulin content in the pancreas were also measured. Immunostainings for insulin and BrdU were performed.
Results. New-onset diabetes could be reversed in 38% of NOD mice treated with CFA alone and in 86% of NOD mice treated with both CFA and exendin-4. Diabetes adoptive transfer by splenocytes from CFA-treated NOD mice was delayed. The percentage of CD4(+)CD25(+)Foxp3(+) regulatory T cells in the pancreatic lymph nodes of CFA-treated NOD mice was significantly increased at 1, 5, and 15 to 17 weeks after treatment. TGF-beta 1 in the plasma of CFA-treated NOD mice was also significantly increased. Combining CFA with exendin-4 treatment significantly increased the insulin content and the numbers of insulin and BrdU double-labeled beta cells in the islets.
Conclusions. Our results demonstrated that CFA treatment ameliorates autoimmunity in diabetic NOD mice by up-regulating CD4(+)CD25(+)Foxp3(+) regulatory T cells and increasing TGF-beta 1 production. Exendin-4 enhanced the effect of CFA on reversing diabetes in NOD mice by stimulating P-cell replication.
