Immunopathological studies of the small intestinal intramural nervous system and of intramural vessels in Crohn's disease.

Widespread damage of the enteric nervous system has been described in Crohn's disease. Using routine microscopy and immunohistochemistry we have studied the presence of the inflammatory infiltrate in relation with the enteric nervous system in small intestinal biopsies from 20 patients with Crohn's disease (9 patients with perforating disease and 11 patients with stricturing disease) and in 10 biopsies from normal small intestine. Routine microscopy shows the presence of a mild inflammatory infiltrate in relation with the components of the nervous system in Crohn's disease. Immunohistochemistry for subtypes of lymphocytes shows that alterations of the enteric nervous system are associated with the presence of T lymphocytes and MHC class II positive monocytes. In addition MHC class II antigens are strongly expressed on components of the enteric nervous system, especially on enteroglial cells. The latter finding is confirmed by immuno-transmission electronmicroscopy. A similar expression can also be found on occasional vascular smooth muscle cells. These changes are associated with a disturbed anatomical distribution of the enteric nervous system and with an increased number of thickened nerve fibers. The strong expression of MHC class II antigens suggests that the alterations of the enteric nervous system in Crohn's disease are the result of an inflammatory process and that they may have an active part in the pathogenesis of the intestinal lesions in Crohn's disease.