Possible role of prostaglandin producing monocytes in the depression of mitogenic responses of blood lymphocytes following radiation therapy.

Previous studies have shown that the depression of mitogenic responses of cultured blood lymphocytes following radiation therapy can largely be explained by immunosuppressive cells. In this investigation we have shown that the addition of silica, a monocyte toxic agent, to the cultures enhance the PHA- and PPD-responses of the cells at completion of irradiation. Such an effect, however, was not noted before radiation treatment was started. Similar results were obtained by adding indomethacin, an inhibitor of prostaglandin synthesis, to the cultures. The results thus indicate that immunosuppressive monocytes which mediate their activity by prostaglandins are involved in the reductions of mitogen responses of blood lymphocytes following irradiation.