Figure 1.

Heterogeneity and functions of steady-state IMCs. (A) In the lamina propria and the muscularis mucosae distinct subsets of IMCs can be found. Directly underneath the epithelium, SEMFs or telocytes form an envelope. Pdgfra^lo stromal cells are dispersed along the crypt–villus length. Close to the muscularis externa and below the crypts, trophocytes form a stripe. Pericytes are found in the perivascular area. (B) SEMFs and trophocytes play a critical role in creating a niche for ISCs by the secretion of Wnt and BMPs. (C) Under steady-state conditions, IMCs not only excel in producing ECM components and matrix remodeling enzymes but also secrete a wide array of immunomodulatory cytokines and chemokines. (D) By the expression of PDL1/2 and MHC-II molecules, IMCs play a critical role in the maintenance of intestinal tolerance. (E) IMCs may induce tolerogenic CD103⁺ dendritic cells and IgA⁺ plasma cells, both of which contribute to intestinal homeostasis.