Thymosin alpha 1 enhancement of human lymphocyte proliferation is not mediated by prostaglandin E2

Prostaglandins of the E series have been implicated as possible mediators of thymosin alpha 1 (TA-1) effect on mitogen stimulated lymphoproliferation. In the present study human peripheral blood mononuclear cells were stimulated with concanavalin A in the presence of TA-1, prostaglandin E2 and indomethacin individually, or in combination. Both TA-1 and indomethacin significantly enhanced the proliferative response over that seen with mitogen alone (less than 0.001). The magnitude of enhancement observed with indomethacin (20 microM) was considerably less than that of TA-1 and it was abolished with prostaglandin E2. The combination of indomethacin and TA-1 did not alter TA-1 effect and prostaglandin E2 (up to 250 ng/ml) did not abolish thymosin effect. These results suggest that TA-1 and prostaglandin E2 have opposite effects and that thymosin enhancement of mitogen induced proliferation is not mediated by prostaglandin E2.