Hine, A. | Search bioRxiv

bioRxiv2020

Transcriptional Atlas of Ileal-Anal Pouch Immune Cells from Ulcerative Colitis Patients

How the human intestinal immune system is distinctly organized to respond to inflammation is still poorly understood. Here, we used single-cell RNA-sequencing to examine lamina propria CD45+ hematopoietic cells from patients with inflammatory bowel disease that have undergone ileal pouch-anal anastomosis, or the colon mucosa of ulcerative colitis patients. We identified a population of IL1B+ antimicrobial macrophages and FOXP3/+BATF+ T cells that are associated and expanded in inflamed tissues, which we further validated in other scRNA-seq datasets from IBD patients. CD8+ T cells were unexpectedly more abundant in the pouch than colon. Cell type specific markers obtained from single-cell RNA-sequencing was used to infer representation from bulk RNA sequencing datasets, which further implicated antimicrobial macrophages expressing IL1B with S100A8/A9 calprotectin as being associated with inflammation, as well as Bacteroides and Escherichia bacterial species. Finally, we find that non-responsiveness to anti-integrin biologic therapies in UC patients is associated with the signature of this antimicrobial macrophage population in a subset of patients. This study identified conserved and distinct features of intestinal inflammation between parts of the small and large intestine undergoing similar inflammation conditions.

immunology↗

bioRxiv2019

Serum Amyloid A Proteins Induce Pathogenic TH17 Cells and Promote Inflammatory Disease

Lymphoid cells that produce IL-17 cytokines protect barrier tissues from pathogenic microbes, but are also prominent effectors of inflammation and autoimmune disease. T-helper (TH17) cells, defined by ROR{gamma}t-dependent production of IL-17A and IL-17F, exert homeostatic functions in the gut upon microbiota-directed differentiation from naive CD4+ T cells. In the non-pathogenic setting, their cytokine production is regulated by serum amyloid A proteins (SAA1 and SAA2) secreted by adjacent intestinal epithelial cells. However, TH17 cell behaviors vary markedly according to their environment. Here we show that SAAs additionally direct a pathogenic pro-inflammatory TH17 cell differentiation program, acting directly on T cells in collaboration with STAT3-activating cytokines. Using loss- and gain-of-function mouse models, we show that SAA1, SAA2, and SAA3 have distinct systemic and local functions in promoting TH17-mediated inflammatory diseases. These studies suggest that T cell signaling pathways modulated by the SAAs may be attractive targets for anti-inflammatory therapies.

immunology↗