CD101 inhibits the expansion of colitogenic T cells

CD101 exerts negative-costimulatory effects in vitro, but its function in vivo remains poorly defined. CD101 is abundantly expressed on lymphoid and myeloid cells in intestinal tissues, but absent from naïve splenic T cells. Here, we assessed the impact of CD101 on the course of inflammatory bowel disease (IBD). Using a T cell transfer model of chronic colitis, we found that in recipients of naïve T cells from CD101(+/+) donors up to 30% of the recovered lymphocytes expressed CD101, correlating with an increased IL-2-mediated FoxP3-expression. Transfer of CD101(−/−) T cells caused more severe colitis and was associated with an expansion of IL-17-producing T cells and an enhanced expression of IL-2Rα/β independently of FoxP3. The co-transfer of naïve and regulatory T cells (Treg) protected most effectively from colitis, when both donor and recipient mice expressed CD101. While the expression of CD101 on T cells was sufficient for Treg-function and the inhibition of T cell proliferation, sustained IL-10-production required additional CD101-expression by myeloid cells. Finally, in patients with IBD a reduced CD101-expression on peripheral and intestinal monocytes and CD4(+) T cells correlated with enhanced IL-17-production and disease activity. Thus, CD101-deficiency is a novel marker for progressive colitis and potential target for therapeutic intervention.