Examining the Immune Composition of the Intestinal Mucosa by Mass Cytometry

Abstract

Abstract BACKGROUND The inflammatory bowel diseases (IBD) can affect various segments of the gastrointestinal tract, and the biology behind regional differences in disease remains poorly understood, in part due to a lack of understanding of regional variation of the particular cell subsets present. By utilizing mass cytometry, our objective was to identify regional differences in the immune composition of the digestive tract in healthy individuals. METHOD Intestinal pinch biopsies were obtained from the following sites of healthy individuals (n=10); duodenum, terminal ileum, ascending colon, transverse colon, descending colon, and rectum. Immune cells were isolated from biopsies and stained with a panel of 37 markers for analysis using mass cytometry. RESULTS Marked variations in immune cell composition were observed along the digestive tract, in particular T and B lymphocytes. Increased abundance of T lymphocytes (>30% of total CD45+ cells) was identified in the duodenum and terminal ileum, whereas B lymphocytes became more abundant (>30% of total CD45+ cells) towards the distal end of the tract. In addition, intestinal homing molecules displayed variation at each site; integrin α4β7, a target for IBD therapeutic intervention, was increasingly expressed in the terminal ileum and ascending colon, compared with the descending colon (Mean 40% vs 25% abundance, n=10, p<0.01). CONCLUSIONS Mass cytometry has the ability to identify and characterize numerous distinct immune subsets throughout the intestinal mucosa, allowing a deep understanding of regional differences in immune composition. This understanding may shed light on the pathogenesis of IBD and allow standardization of intestinal sampling during the evaluation of therapeutics.