IL-10 enhances T cell survival and is associated with faster relapse in patients with inactive ulcerative colitis

Ulcerative colitis (UC) is characterized by a relapsing and remitting pattern. The remission phase may last weeks to years. It remains unclear what specific factors can cause the disease to exist the remission phase and enter an activated state. IL-10 is a cytokine best known for its anti-inflammatory roles. We hypothesized that IL-10 might have a role in suppressing disease flares in UC remission patients. Unexpectedly, we found that UC remission patients with higher serum IL-10 levels presented faster progression to disease flares. Subsequently, we found that exogenous IL-10 could significantly reduce the level of CD4 and CD8 T cell proliferation. On the other hand, IL-10 significantly elevated the viability of activated CD4 and CD8 T cells. Interestingly, it appeared that the IL-10-mediated pro-survival effects were more pronounced in CD8 T cells than in CD4 T cells and were able to promote the survival of activated T cells when administered prior to cell activation. To examine whether IL-10 in the serum of UC patients was able to enhance T cell survival, we separated UC remission patients into Low, Intermediate, and High groups based on the serum IL-10 level. The native serum from High IL-10 patients, but not the native serum from Low IL-10 patients, could significantly increase the viability of activated T cells. In conclusion, we demonstrated that high IL-10 level at the remission phase was associated with shorter duration of remission, possibly due to IL-10-mediated effects on T cell survival.