Author: Sasson S.C. (sarah.sasson@ndm.ox.ac.uk); Cheung V.T.F.; Gupta T.; Klenerman P.; Brain O.; Zaunders J.J.; Kelleher A.D.; Nahar K.; Scolyer R.A.; Carlino M.S.; Long G.V.; Menzies A.M.; Munier C.M.L.; Fairfax B.P.; Payne M.J.; Olsson-Brown A.; Jolly C.; Read S.A.; Ahlenstiel G.; Palendira U.
Abstract: The aim of this study was to investigate the pathogenesis of combination ipilimumab and nivolumab-associated colitis (IN-COL) by measuring gut-derived and peripheral blood mononuclear cell (GMNC; PBMC) profiles. We studied GMNC and PBMC from patients with IN-COL, IN-treated with no adverse-events (IN-NAE), ulcerative colitis (UC) and healthy volunteers by flow cytometry. In the gastrointestinal-derived cells we found high levels of activated CD8+ T cells and mucosal-associated invariant T (MAIT) cells in IN-COL, changes that were not evident in IN-NAE or UC. UC but not IN-C was associated with a high proportion of regulatory T cells (Treg). We sought to determine if local tissue responses could be measured in peripheral blood. Peripherally, checkpoint-inhibition instigated a rise in activated memory CD4+ and CD8+ T cells, regardless of colitis. Low circulating MAIT cells at baseline was associated with IN-COL patients, compared with IN-NAE in one of two cohorts. UC but not IN-COL was associated with high levels of circulating plasmablasts. In summary, the alterations in T cell subsets measured in IN-COL-affected tissue, characterised by high levels of activated CD8+ T cells and MAIT cells and a low proportion of Treg, reflected a pathology distinct from UC. These tissue changes differed from the periphery, where T cell activation was a widespread on-treatment effect, and circulating MAIT cell count was low but not reliably predictive of colitis (Figure1).
