TNF and diabetes mellitus: F4/80(+) peritoneal exudate macrophages (PEMs) from mice with diabetes for 4 months displayed significantly reduced proinflammatory cytokines TNF-α and IL-6 production but enhanced nitric oxide (NO) secretion when treated with IFN-γ and LPS, while the activity of arginase in PEMs from diabetic mice was significantly higher than control mice when stimulating with IL-4 [26].