Phenotypic characterization of isolated intraepithelial lymphocytes in patients with ulcerative colitis and normal controls.

A method was developed to isolate colonic intraepithelial lymphocytes in patients with ulcerative colitis (N = 8) and normal controls (N = 13) in order to characterize their phenotype using a panel of monoclonal antibodies and flow cytometry. In both groups, the majority of the cells are of the CD3+CD8+ phenotype associated with cytotoxic/suppressor function. The CD4/CD8 ratios were similar. Virtually no B cells or macrophages were found. An increase in cells coexpressing the CD3 and HLA-DR molecules and a decrease in natural killer cells (CD3, CD16+CD56+) were found in ulcerative colitis, but this was not significant. There were no differences in the proportions of CD8+ and CD4+ cells expressing the Leu8 antigen between ulcerative colitis and controls. Thus a population of colonic intraepithelial lymphocytes has been isolated and, although they may be functionally different in ulcerative colitis compared with controls, this cannot be explained in terms of phenotypic characteristics.