Immunohistochemical studies of ulcerative colitis--expression of HLA-DR antigen by colonic epithelium and the role of dendritic cells in the lamina propria

In 27 patients with ulcerative colitis the colonic mucosa was analyzed by an immunohistochemical technique. A quantitative evaluation for lymphocyte subsets shows significantly-increased numbers of CD3+ cells, CD4+ cells, CD8+ cells and Leu7+ cells in ulcerative colitis cases of histological grades 4 and 5 by Matts's classification comparing to controls. However, CD4/CD8 ratio in each histological grade of ulcerative colitis was similar to that in normal controls. The HLA-DR antigen on the colonic epithelium was frequently expressed in patients with grades 3 to 5 (84.2%), and in active patients (88.9%). The antigens were also expressed on the lamina propria mononuclear cells, which coincided with the distribution of S-100+ dendritic cells. Moreover double staining for S-100 antigen and IL-2R antigen revealed that most of the S-100+ dendritic cells were also IL-2R positive. These findings seem to provide evidence for the important role of lamina propria dendritic cells in the immunological pathogenesis of ulcerative colitis.