Frequencies of circulating regulatory TIGIT + CD38 + effector T cells correlate with the course of inflammatory bowel disease.

Disease heterogeneity hampers achieving long-term disease remission in inflammatory bowel disease (IBD). Monitoring ongoing tissue-localized regulatory and inflammatory T-cell responses in peripheral blood would empower disease classification. We determined whether regulatory and inflammatory phenotypes of circulating CD38+ effector (CD62Lneg CD4+ ) T cells, a population enriched for cells with mucosal antigen specificity, classify disease course in pediatric IBD patients. In healthy individuals, circulating CD38+ effector T cells had a predominant regulatory component with lower frequencies of IFNγ-secreting T cells, higher frequencies of IL-10-secreting T cells and higher frequencies of inhibitory molecule T-cell immunoglobulin and ITIM domain+ (TIGIT) cells than CD38neg effector T cells. TIGIT expression was stable upon stimulation and marked CD38+ T cells with inhibitory properties. In IBD patients with active intestinal inflammation this predominant regulatory component was lost: circulating CD38+ effector T cells had increased activated CD25+ CD45RAneg and decreased TIGIT+ cell frequencies. TIGIT percentages below 25% before treatment associated with shorter duration of clinical remission. In conclusion, phenotypic changes in circulating CD38+ effector T cells, in particular the frequency of TIGIT+ cells, classify pediatric IBD patients and predict severity of disease course. These findings have relevance for IBD and can be exploited in graft-versus-host-disease and checkpoint inhibitor-induced inflammation in cancer.