A new paradigm in ulcerative colitis: Regulatory T cells are key factor which induces/exacerbates UC through an immune imbalance

Leukocytapheresis (LCAP) appears to remove or inactivate inflammatory cells and to reset immunological responses, resulting to cure responders of ulcerative colitis (UC). The changes of T cell subsets were investigated in UC patients treated with LCAP. Levels of T cell subsets in peripheral blood before and after LCAP were analysed by flow cytometric analysis. Of 20 UC patients, 13 (65%) achieved remission and 2 (10%) showed the improvement of UC symptoms. Ratios of some T cell subtypes such as regulatory T (Treg) cells and memory T cells to CD4+ T cells changed significantly only in responders. Especially, ratio of resting Treg/CD4+ T cells was significantly increased after the first LCAP session, and then one of activated Treg/CD4+ T cells was increased after 2 week. This may lead to the development of a new UC paradigm in which an imbalance in Treg cell subsets triggers the onset and/or exacerbation of UC.

► In patients with ulcerative colitis, the rate of resting Treg cells was significantly increased after the first LCAP treatment.
► The rate of activated Treg cells was significantly higher than that of resting Treg cells after the fifth treatment.
► The balance between resting/activated Treg cells and inflammatory T cells was normalized after induction remission.