Increased Th17-inducing activity of CD14⁺ CD163^low myeloid cells in intestinal lamina propria of patients with Crohn's disease

Background & Aims Abnormal activity of innate immune cells and T-helper (Th) 17 cells has been implicated in the pathogenesis of autoimmune and inflammatory diseases, including Crohn's disease (CD). Intestinal innate immune (myeloid) cells have been found to induce development of Th17 cells in mice, but it is not clear if this occurs in humans or in patients with CD. We investigated whether human intestinal lamina propria cells (LPCs) induce development of Th17 cells and whether these have a role in the pathogenesis of CD. Methods Normal intestinal mucosa samples were collected from patients with colorectal cancer and noninflamed and inflamed regions of mucosa were collected from patients with CD. LPCs were isolated by enzymatic digestion and analyzed for expression of HLA-DR, lineage markers CD14 and CD163 using flow cytometry. Results Among HLA-DR^high Lin^- cells, we identified a subset of CD14⁺ CD163^low cells in intestinal LPCs; this subset expressed Toll-like receptor (TLR) 2, TLR4, and TLR5 mRNAs and produced interleukin (IL)-6, IL-1β, and tumor necrosis factor in response to lipopolysaccharide. In vitro co-culture with naïve T cells revealed that CD14⁺ CD163^low cells induced development of Th17 cells. CD14⁺ CD163^low cells from inflamed regions of mucosa of patients with CD expressed high levels of IL-6, IL-23p19, and tumor necrosis factor mRNAs, and strongly induced Th17 cells. CD14⁺ CD163 ^low cells from the noninflamed mucosa of patients with CD also had increased abilities to induce Th17 cells compared with those from normal intestinal mucosa. Conclusions CD14⁺ CD163^low cells in intestinal LPCs from normal intestinal mucosa induce differentiation of naive T cells into Th17 cells; this activity is increased in mucosal samples from patients with CD. These findings show how intestinal myeloid cell types could contribute to pathogenesis of CD and possibly other Th17-associated diseases.