Immunohistochemical and electronmicroscopic observations on the local immune response in ulcerative colitis.

Inflammatory cell infiltrates in ulcerative colitis have been investigated by means of the immunoperoxidase method and by electronmicroscopy. Considerable morphological and functional changes of the local plasma cell population have been found. The absolute number of plasma cells is raised with a marked increase of IgG-cells and a relative decrease of IgA-cells. In particular complement (C3) has been demonstrated at the basement membrane of the surface epithelium and between epithelial cells. The significance of these findings, as a local humoral immune response, is briefly considered, with regard to their possible pathogenetic importance in aggravating and perpetuating the disease.