Impaired mitogenic response of peripheral blood T cells in ulcerative colitis is not due to apoptosis

An abnormal immune response may play a pathogenic role in ulcerative colitis (UC). Animal models suggest that T-cell regulation may be of central importance in the inflammatory process, Our aims were the characterization of the phenotype and functional status of circulating T-cells in ulcerative colitis patients and to determine if activation-induced cell death in CD4(+) and CD8(+) lymphocytes in patients differs from healthy controls. Forty-eight patients (24 women and 24 men) fulfilling the histopathological, clinical, and immunological criteria for UC were studied. T-cell phenotype and function were studied in blood lymphocytes from patients with ulcerative colitis and healthy donors by flow cytometric analysis, as well as [H-3]thymidine incorporation, There were no significant differences in the percentage of T-cell subpopulations (CD3, CD4, CD8) and NK cells in the different groups. The percentage of cells in growth phase S+G(2)M at two and three days of phytohemagglutinin (PHA) stimulation was significantly decreased in UC patients, but the percentage of CD4(+) and CD8(+) cells in UC patients that showed apoptosis was not significantly different than that in the control group. Proliferative responses to IL-4 also suggested that a reduced responsiveness to this cytokine may be involved in UC, III conclusion, the impaired proliferative response to PHA of T lymphocytes from UC patients is not associated with an in vitro increase in the apoptotic response in CD4(+) or CD8(+) cells. A reduced IL-4 response may be involved in this peculiar mitogenic response These changes may be pathogenic or a favorable adaptive mechanism.