TNF and Chronic colitis: Furthermore, a rat model of ulcerative colitis demonstrated that swimming attenuated dextran sulfate sodium-induced chronic colitis, as reflected by reduction in colon shortening, fecal calprotectin levels, activated CD3+ T cell abundance within the lamina propria, and proinflammatory serum cytokine levels including tumor necrosis factor (TNF), interleukin (IL)-1β and IL-6, with an increase in serum levels of IL-10, an immunosuppressive cytokine (29).