Ultrastructural study of relationships between c-kit immunoreactive interstitial cells and other cellular elements in the human colon

C-E;it immunocytochemistry was performed on ultrathin sections of human dis tal colon. Our attention was focused on relationships between c-kit immunor eactive interstitial cells (c-kit ICs) and muscular cells and nervous eleme nts located in the external muscular layers of the colonic wall. C-kit ICs established membrane apposition with both nerve fibers and smooth muscle ce lls of, respectively, the longitudinal and circular muscle layers, the myen teric area, and the extremus submucosus plexus. C-kit ICs also surrounded t he external submucosus plexus and established membrane appositions with ner ve elements located inside the myenteric ganglia. These membrane apposition s were observed either at the level of the c-kit IC bodies or at that of th eir cytoplasmic processes. In some cases, membrane appositions were observe d concomitantly between the c-kit ICs, nerve fibers, and smooth muscle cell s. In all the regions studied, the c-kit ICs were also found to be located in the close vicinity of blood vessels and to have established close contac ts with non-immunoreactive fibroblast-like cells. The results of the presen t study shed essential light on the relationships of c-kit ICs with the nei ghboring muscle cells and nerve elements, and confirm that the intercalated c-kit ICs well fit with the so-called "interstitial cells of Cajal".