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 intraepith elial lymphocytes at the transcriptional level with HLA-DR(+) human co lonic epithelial cell line (HT29) in synergy with CD3 monoclonal antib ody and to investigate the molecular mechanism for the therapeutic eff ects of 5-aminosalicylic acid. Lymphocytes were isolated by a mechanic al method from resected colon of 22 cases and then cocultured on 10 ng /ml CD3mAb immobilized plates with HT29 which had been induced to expr ess MHC class II molecules by interferon gamma. Flow cytometry analysi s 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 transc ription of interferon gamma and tumor necrosis factor alpha, as measur ed by means of the reverse-transcriptase polymerase chain reaction, an d this activation was antagonized by 5-aminosalicylic acid. Thus, epit helial cells bearing HLA-DR are capable of enhancing CD3-induced activ ation of human colonic intraepithelial lymphocytes and subject to inhi bition by 5-aminosalicylic acid, the active moiety of salicylates used in inflammatory bowel disease.