BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages 86-93 STIMULATION OF PROSTAGLANDIN E AND THROMBOXANE B ^ PRODUCTION BY HUMAN MONOCYTES IN ~SPONSE TO INTERLEU~IN-2

Interleukin 2 (IL-2) 1 is a potent lymphokine involved in the regula-tion of immune responses and is classically regarded as a stimulus for the activation and growth of T-cells. Recent reports have demonstrated the IL-2 dependent activation of human peripheral blood lymphocytes into lymphokine activated killer cells capable of lysing tumor cells both in vitro and in vivo. In this study we report data which clearly show IL-2 may also act to down-regulate the immune response by inducing the synthe-sis of arachidonic acid metabolites with known immunosuppressive actions. Stimulation of peripheral human blood monocytes with IL-2 caused an increased production of prostaglandin E ^ (PGE^) and thromboxane (TXB2) •.. z. z in a dose-dependent manner • Kinetic analysis showed no increase above controls after 6 hours and maximal levels by I0 hours; elevated levels were maintained after 45 hours of incubation. After 20 hours of stimula-tion with 2000 U/ml IL-2, the level of PGE2 nnd TXB were greater than 5 2 three-fold above controls, 0.7 and 19 ng/10 cells, respectively. Th