Prediction of steroid demand in the treatment of patients with ulcerative colitis by immunohistochemical analysis of the mucosal microenvironment and immune checkpoint: role of macrophages and regulatory markers in disease severity.

We aimed to characterize the mucosal immune microenvironment and immune checkpoint of Ulcerative colitis (UC) by immunohistochemistry with correlation to prognosis: requirement of second-line steroid-therapy within the 2-years after diagnosis (SR). A series of 72 cases included 56 UC, 43 non-SR (with first-line treatment 5-ASA) and 13 SR, 11 infectious colitis and 5 normal colonic biopsies. Normal mucosa was characterized by low infiltrates but high BTLA and TNFRSF14. Compared to normal, UC had increased pan-immune-markers of CD3, CD8, FOXP3, PD-1, CD68, CD16, CD163, PTX3 and CD11C but had decreased BTLA (P < 0.05); by GSEA analysis comparable results were found in an independent UC gene-expression-data set (GSE38713). Compared to infectious, UC had higher CD4, CD8, PTX3 and CD11C but lower BTLA (P < 0.05). Compared to non-SR, SR had lower FOXP3 + Tregs (Odds-Ratio = 0.114, P = 0.002), PD-1 (OR = 0.176, P = 0.002) and CD163/CD68 M2-ratio (OR, 0.019, P = 0.019) but higher CD68 + pan-macrophages (OR = 6.034, P = 0.002). Higher Baron endoscopic and Geboes histologic disease activity scores also correlated with SR. In summary, UC was characterized by increased pan-immune-markers, normal TNFRSF14 and low BTLA. SR had increased CD68 + pan-macrophages but lower immune inhibitors of FOXP3 + Tregs, PD-1 and CD163/CD68 M2-macrophage ratio. In conclusion, alterations of the immune homeostasis mechanisms are relevant in the UC pathogenesis and steroid-requiring situation.