Prostaglandin E2 regulation of human specific B-cell response: interaction with a monocyte product

The effect of exogeneous prostaglandin E2 (PGE2) on the specific plaque-forming cell (PFC) response in cultures of non-adherent human peripheral blood mononuclear cells (PBM) was tested. When added on Day 2 of the cultures PGE2 inhibits the induction of the PFC response, and the maximum inhibition (50%) is obtained with 300 nM PGE2. When PBM are cultured during the first 24 hr with the same concentration of PGE2 their PFC response is enhanced and the target of this enhancement is a T cell. When PGE2 is added on Day 0 it does not affect the response, probably because of a balance between these two opposing effects. However, in the latter conditions a prostaglandin-free monocyte supernatant can render PGE2 suppressive. The monocyte supernatant acts by inhibiting the stimulatory effect after the interaction between PGE2 and T cells. Thus the effect of PGE2 depends on its time of action and on the concomitant production of a nondialyzable factor by monocytes.