Suppressor effect of prostaglandins on T colony formation

This study evaluated the action of prostaglandins on T colony formation. A single step culture process was used which involved direct seeding of freshly isolated peripheral blood mononuclear cells (MC) in semi-solid agar culture medium containing phytohaemagglutinin (PHA). Suppression of endogenous production of prostaglandins with 10(-6) M indomethacin increased T colony formation by up to 100%. Similarly, addition of synthetic prostaglandin E (PGE) to the culture system demonstrated a dose-dependent reduction of T colony formation by PHA-stimulated non-adherent cells. The 50% inhibitory dose (ID 50) was 10(-7) M for PGE2 and 1.3 x 10(-7) M for PGE1. Prostaglandin F had no effect on T colony formation. The synthesis of PGE by adherent cells can be increased two- to three-fold in the presence of T colony promoting activity released by PHA-stimulated lymphocytes. We conclude that monocyte produced PGE is responsible for the suppressor effect exerted by these cells on T colony formation. The PGE inhibitory role is interpreted as a feedback mechanism, modulated by lymphokines released by PHA-activated lymphocytes.