The effects of indomethacin on T lymphocyte stimulation.

Immunomodulatory effects of indomethacin on mitogen-induced [3H]thymidine incorporation in cultured pig peripheral blood lymphocytes were demonstrated. In monocyte-containing lymphocyte cultures, indomethacin enhanced lymphocyte stimulation, whereas in monocyte-depleted cultures indomethacin inhibited the response. Indomethacin effects were most marked at suboptimal to optimal concentrations of mitogen and decreased at superoptimal concentrations in both types of culture. The effects of prostaglandin E2 at superoptimal mitogen concentrations were found paradoxically to be stimulatory. The results indicate that arachidonic acid metabolites may have both positive and negative effects on lymphocyte activation.