The distribution of mucosal antibodies in the bowel of patients with Crohn's disease.

Specimens of intestine from 24 patients with histologically proven Crohn's disease have been studies by an immunofluorescent technique for the distribution of immunoglobulins A, G, M, E, and D. A marked reduction of IgA in lymphoid and epithelial cells was noted in those areas of the bowel which, although histologically affected, were not ulcerated; in the histologically unaffected areas of the bowel the distribution of IgA was similar to that found in control sections of normal bowel. There was an increase in IG7 in the affected areas but the numbers of lymphoid cells staining for IgD did not differ from those found in normal controls; in 12 cases of Crohn's disease, however, IgG appeared to be present in bound form on the surface of, and in, the epithelial cells. It is postulated that the local deficiency in IgA in the affected areas may be secondary to a local cell-mediated immune reaction, to a focal metaplasia of the surface epithelium, or to patchy bindings of anticolon antibodies to the surface epithelium. The effect of this local deficiency of IgA will be to allow for an increased focal entry of antigenic material into the bowel wall, and it is suggested that many of the pathological features of Crohn's disease are explicable on the basis of deep penetration of a variety of antigens.