Distribution of mucosal PD-1 expressing T cells in patients with colitis of different etiologies
Britt Roosenboom, Carmen S. Horjus Talabur Horje, Carolijn Smids, Jan Willem Leeuwis, Elly van Koolwijk, Marcel J. M. Groenen, Peter J. Wahab, Ellen G. van Lochem
Abstract
Background Immunotherapy, targeting programmed death-1 (PD-1) enhances antitumor T-cell activity in patients with malignancies. Blocking PD-1 or its ligand may lead to fulminant colitis as serious adverse event in these patients. Since little is known of the presence and role of PD-1+T cells in colitis of different etiologies, we determined PD-1+T cells in mucosal specimens of patients with inflammatory bowel disease, infectious colitis (InfC), immunotherapy-related colitis (ImC) and healthy controls (HC).Methods Newly diagnosed patients with ulcerative colitis (UC, n = 73), Crohn’s disease (CD, n = 50), InfC (n = 5), ImC (n = 8) and HC (n = 8) were included. Baseline inflamed colonic biopsies were studied with immunohistochemistry and flowcytometry.Results Using immunohistochemistry, PD-1 was not present on lymphocytes in the epithelium of all patients, nor in HC. The percentage PD-1+ of all lymphocytes in the lamina propria was 40% in UC, 5% in InfC, 3% in ImC and 0% in HC. Flowcytometry showed significant higher percentages of PD-1+T cells in inflamed biopsy specimens of UC patients (22%) compared to all other groups: CD patients (13%), InfC (12%), ImC (5%) and HC (6%).Conclusion There are relevant differences in distribution and frequencies of mucosal PD-1+ T-cell subsets in patients with UC, CD, InfC and ImC, supporting the hypothesis that these types of colitis are driven by different immunological pathways. The increased numbers of PD-1+ and PD-L1+ lymphocytes in the colonic mucosa of UC patients suggest that the PD-1/PD-L1 pathway might be more activated in UC than in CD.