P007 Neutrophil function in lesional biopsies is a strong determinant of IBD severity and may relate to an altered functional state already present in circulating cells

Abstract

Abstract Background Neutrophils clear luminal bacteria from the intestinal lamina propria and have a protective role in Inflammatory Bowel Disease (IBD). However, their production of inflammatory cytokines, matrix metalloproteases and radical oxygen species causes irreversible tissue damage. Histological assessment of infiltrating neutrophils and indirect measurement of neutrophil-derived calprotectin in feces are used to assess disease severity in patients. Since IBD is a heterogeneous disease in terms of presentation, severity and course, we hypothesize that different patients have a different composition of their neutrophil compartment that leads to a different balance between protection and damage. We aim to study the variability in neutrophil phenotype and function and relate it to patient heterogeneity. Methods We analyzed endoscopic biopsies and peripheral blood samples from children diagnosed with IBD within the PIBD-SETQ cohort. Paired biopsies obtained at diagnosis were scored by a pathologist and analyzed by IHC and RNAseq. RNAseq was also performed on purified circulatory neutrophil at diagnosis and their phenotype was analyzed by whole-blood flow cytometry. Results At diagnosis, high numbers of infiltrating neutrophils in intestinal tissue differentiated IBD patients with high clinical disease activity, more severe endoscopic and histological disease and high plasma concentrations of IL-17. RNA sequencing of lesional intestinal biopsies revealed differential expression of genes linked to neutrophil degranulation and IL-17 signaling in the colon of IBD patients with high neutrophil infiltration. Moreover, these biopsies had high mRNA expression for Oncostatin M, a neutrophil product known to associate with therapy resistance. To assess whether circulating neutrophils were altered in IBD before entering the intestinal tissue, we performed bulk RNAseq analysis of purified circulating neutrophils from non-IBD and CD patients. Neutrophils from CD patients had increased expression of genes related to granule formation and filling (MMP9, S100A8, S100A9) and pathogen sensing (TLR5, NLRC4) but not cytokine production (IL1B, OSM), relative to non-IBD patients. Expression of CD10 was decreased in circulating neutrophils from UC and CD patients while CD16 expression was lower in UC-derived neutrophils, suggesting these cells have a more immature state. Conclusion We have detected changes in the maturity of neutrophils in the circulation of some IBD patients that could have functional consequences in terms of bacterial clearance and tissue damage in the intestinal mucosa. Uncovering different functional profiles in neutrophils may help dissect patient heterogeneity and provide novel targets for therapy.