P052 IL-12p70 as a potential driver of pathogenic IL-17+IFNγ+ mucosal memory TIGITneg T cells in a subgroup of severe CD patients

Abstract

Abstract Background Crohn’s disease (CD) is a chronic disease driven by inflammatory memory CD4+ T cells. Deciphering heterogeneity in underlying immune disease is required for predicting the individual patients’ disease course. We have shown that analysis of circulating CD38+ memory CD4+ T cells, which are enriched for gut-homing, identifies therapy-naïve pediatric CD patients with a more severe disease course. At diagnosis, these patients have increased frequencies of circulating CD38+ memory T cells that do not express TIGIT (TIGITneg). TIGIT (T-cell immunoreceptor with immunoglobulin and ITIM domains), is a coinhibitory receptor selectively induced on CD4+ T cells with a memory phenotype. In healthy controls, TIGIT+CD38+ memory T cells have an inhibitory function while TIGITnegCD38+ memory T cells are enriched in inflammatory cells. In our cohort of CD patients, circulating inflammatory TIGITnegCD38+ memory T cells had increased frequencies of pathogenic IFNγ +IL-17+-double-producing or Th1* cells. We hypothesize that in these severe CD patients, CD-related inflammatory cytokines selectively increase frequencies of Th1* TIGITnegCD38+ memory T cells. Methods We cultured peripheral blood memory CD4+ T cells from healthy individuals in vitro with TCR- and co-stimulation together with different cocktails of CD-related inflammatory cytokines during 72h. Results Of all cytokines tested, only cocktails containing IL-12p70 increased TIGITneg cell frequencies within gut-homing CD38+ memory T cells, but not CD38neg memory T cells that are enriched in skin-homing. As hypothesized, IL-12p70-stimulated cultures contained higher frequencies of Th1* cells, expressing both hallmark transcription factors T-bet and RORgt, in TIGITnegCD38+ T cells but not within TIGIT+CD38+ T cells. This selective IL-12p70 responsiveness in TIGITneg cells agreed with the higher expression of the IL-12 receptor b2 subunit in TIGITnegCD38+ compared to TIGIT+CD38+ memory T cells. These data argue that IL12p70 initiates reprogramming of the TIGITnegCD38+ memory T cells to the Th1* phenotype. To assess whether IL-12p70 causes expansion of TIGITnegCD38+ cells or downregulates TIGIT expression on TIGIT+CD38+ cells, we traced fluorescently-labelled TIGIT+ cells during culture. TIGIT+ cells did not downregulate TIGIT, indicating that IL-12p70 increased proliferation of TIGITnegCD38+ cells. Conclusion The finding that IL-12p70 drives expansion of TIGITnegCD38+ memory T cells with a pathogenic Th1* phenotype argues that this cytokine may enforce chronic inflammation in these severe CD patients. These analyses pave the way toward deciphering key actors involved in CD inflammation at an individual patient level, needed to tailor novel IL-12/IL-23 targeting therapeutic strategies.