Single-cell transcriptomic profile of innate cell populations in mesenteric lymph nodes of inflammatory bowel disease patients

Innate immune cells, including dendritic cells (DCs), monocytes (Mono), macrophages (Mac), natural killer (NK) and innate lymphoid cells (ILC), contribute to chronic inflammation in lymphoid tissues. Here, we characterized the innate immune cell landscape in inflamed mesenteric lymph nodes (MLNs) of patients with inflammatory bowel diseases (IBD) at the single-cell level. CITE-seq analysis unveiled the molecular signature of 11 Mono/Mac/DC (MMDC) and 7 NK/ILC enriched clusters in human MLNs. DC clusters included 3 newly characterized DC clusters: CD1c/CD163/VCAN/CD64-expressing DC3; AXL-expressing DCs; and a CD103+ DC subset, expressing LTB, S100B, and IL22RA2 (encoding IL22BP). Mono/Mac clusters comprised inflammatory monocytes, which accumulated in IBD compared to non-IBD MLNs. Among NK/ILC clusters, we identified a cytotoxic ILC subset (IL7R, KLRD1, GNLY), previously not reported in MLNs, reminiscent of cytotoxic ILC1-like cells found in inflamed gut mucosa. Overall design: Surgically resected colonic MLNs were obtained from patients with Crohn's disease (CD; n=3), ulcerative colitis (UC; n=3), non-inflamed UC (n=1) and non-IBD (n=2). CD45+CD3-CD19- non-T/non-B cells were FACS-sorted to capture rare innate immune cells. Cellular Indexing of Transcriptomes and Epitopes by Sequencing (CITE-seq) was performed on the BD RhapsodyTM platform alongside multiparameter flow-cytometry staining.