IL-12 and Mucosal CD14+ Monocyte-Like Cells Induce IL-8 in Colonic Memory CD4+ T Cells of Patients With Ulcerative Colitis but not Crohn’s Disease

Abstract

Background and Aims CD14+ mononuclear phagocytes [MNPs] and T cells infiltrate colon in ulcerative colitis [UC]. Here we investigated how CD14+ MNPs and the cytokines they produce shape the colonic effector T cell profile. Methods Colonic or mesenteric lymph node [mLNs] CD4+ T cells isolated from UC or Crohn’s disease [CD] patients were stimulated with cytokines or autologous CD14+ MNPs. Cytokine expression was assessed by intracytoplasmic staining and multiplex ELISA. Unsupervised phenotypic multicolour analysis of colonic CD14+ MNPs was performed using the FlowSOM algorithm. Results Among CD14+CD64+HLA-DR+SIRPα + MNPs, only the pro-inflammatory cytokine-producing CD163− subpopulation accumulated in inflamed UC colon and promoted mucosal IL-1β-dependent Th17, Th17/Th1, Th17/Th22 but not Th1 responses. Unsupervised phenotypic analysis of CD14+CD64+ MNPs segregated CD163− monocyte-like cells and CD163+ macrophages. Unexpectedly, IL-12, IL-1β and CD163−, but not CD163+, cells induced IL-8 expression in colonic CD4+ T cells, which co-expressed IFN-γ and/or IL-17 in UC and not CD. The CD163− monocyte-like cells increased the frequency of IL-8+IL-17+/−IFN-γ +/− T cells through IL-1β and IL-12. Finally, colonic IL-8+ T cells co-expressing GM-CSF, TNF-α and IL-6 were detected ex vivo and, promoted by IL-12 in the mucosa and mLNs in UC only. Conclusions Our findings established a link between monocyte-like CD163− MNPs, IL-12, IL-1β and the detection of colonic memory IL-8-producing CD4+ T cells, which might all contribute to the pathogenesis of UC.

Human Intestinal Mononuclear Phagocytes in Health and Inflammatory Bowel Disease

“…It is now clear that the frequency and number of Mfs among intestinal LP cells is increased in IBD patients compared to controls, especially in active lesion areas (132,221,223,225,226,228,246,263,(267)(268)(269)(270)(271)(272) (Figure 5E). More specifically, the augmentation of intestinal Mfs is due to an increase in the frequency of immature Mfs among LP cells, despite that somewhat different surface markers and combinations thereof have been used to characterized them (i.e., HLA-DR or CD11c levels; scRNA-seq) (132,221,223,225,226,228,256,263,270,(272)(273)(274)(275) (Figure 5F). This accumulation seems to be due to the inflammatory intestinal microenvironment of IBD patients, which boosts the recruitment of classical monocytes through mechanisms involving CCL2, IL-8, and TGF-β signaling (223,276).…”

“…This seems to be due to immature Mf accumulation within the total Mf population in Crohn's patients. Indeed, Chapuy et al have recently shown that immature Mfs from IBD patients, but seemingly not mature Mfs, induce Th17 cells, as well pathologic IFN-y + IL-17 + T cells (303), from autologous colonic CD4 + T cells mainly through their production of IL-1β (228,272). Corroborating this, Martin et al have shown that, while initial steps of lymphocyte aggregate formation depend on DCs, immature Mfs likely participate in T cell activation in situ (263).…”

Single-Cell Protein and RNA Expression Analysis of Mononuclear Phagocytes in Intestinal Mucosa and Mesenteric Lymph Nodes of Ulcerative Colitis and Crohn’s Disease Patients

“…In CD and UC patients, both CD163 − and CD163 + MNPs produced pro-inflammatory cytokines (IL-1β, IL-6, IL-12p40, and IL-23). CD163 + MNPs expressed more TNF-α and IL-10 than CD163 − MNPs, which are the major contributors to IL-23 and IL1β [31,39]. The CD163 − , but not CD163 + , MNPs promoted Th17 and Th17/Th1 memory responses in an IL-1β-dependent manner [31,39], which have been suggested to be pathogenic in IBD [40][41][42][43].…”

“…Stratification of colonic CD14 + MNPs according to CD64 and CD163 expression allowed the discrimination of two phenotypically, morphologically, and functionally distinct populations in IBD patients. Only CD14 + CD64 + CD163 −/dim , and more particularly CD163 − but not CD163 + cells, accumulated in inflamed mucosa of IBD patients in proportions that correlate with endoscopic disease severity in CD, regardless treatment history, demographics and disease behavior or location [31,39]. CD14 + CD64 + CD163 − MNPs displayed monocyte morphology, whereas CD163 + MNPs resembled Mφ with cytoplasmic vacuoles [31].…”

“…CD14 + MNPs include HLA-DR high CD163 + Mφ, HLA-DR dim MNPs, HLA-DR + CD64 + cells, and HLA-DR + SIRPα + cells. The latter, which comprises more than 95% of CD14 + cells, was shown to accumulate in the inflamed colon in large cohorts of CD and UC patients compared to paired non-inflamed colon, healed mucosa of IBD patients in endoscopic remission, healthy colon of control donors, or inflamed colons of non-IBD patients [31,39]. Stratification of colonic CD14 + MNPs according to CD64 and CD163 expression allowed the discrimination of two phenotypically, morphologically, and functionally distinct populations in IBD patients.…”