Cytokine gene transcription of human colonic intraepithelial lymphocytes costimulated with epithelial cells bearing HLA-DR and its inhibition by 5-aminosalicylic acid

The objectives of this study were to activate human colonic intraepithelial lymphocytes at the transcriptional level with HLA-DR(+) human colonic epithelial cell line (HT29) in synergy with CD3 monoclonal antibody and to investigate the molecular mechanism for the therapeutic effects of 5-aminosalicylic acid. Lymphocytes were isolated by a mechanical method from resected colon of 22 cases and then cocultured on 10 ng/ml CD3mAb immobilized plates with HT29 which had been induced to express MHC class II molecules by interferon gamma. Flow cytometry analysis suggested that the lymphocyte population had a CD4/CD8 ratio similar to that observed in intact tissue sections and that there was no HT29 contamination of the lymphocytes isolated again from cocultured cells. The activation of intraepithelial lymphocytes showed the gene transcription of interferon gamma and tumor necrosis factor alpha, as measured by means of the reverse-transcriptase polymerase chain reaction, and this activation was antagonized by 5-aminosalicylic acid. Thus, epithelial cells bearing HLA-DR are capable of enhancing CD3-induced activation of human colonic intraepithelial lymphocytes and subject to inhibition by 5-aminosalicylic acid, the active moiety of salicylates used in inflammatory bowel disease.