The effect of prostaglandin metabolism on immunoglobulin and antibody production in naive and educated whole spleen cells

Augmentation of cytotoxic responses by prostaglandin E2

The cytotoxic-T-lymphocyte activity in the spleen cells after in vivo immunization of C3H mice with allogeneic spleen cells ip was consistently very weak. Substantial cytotoxic responses were obtained, however, when prostaglandins (PGE2, PGE1, or PGI2) were injected ip together with or prior to the immunization. An augmentation of cytotoxic responses against allogeneic stimulator cells was also observed in mixed lymphocyte cultures which were provided with an interleukin 2-containing helper factor. This augmentation was observed when PGE2 was added at the start of the culture but not if added 1 day later. Indomethacin was found to be suppressive in these cultures.

Regulation of the immune response by prostaglandins

Of all the arachidonic acid metabolites, only prostaglandin E (PGE) has been shown to have a clear role in the regulation of cellular and humoral immune responses. In cellular immune responses such as T cell proliferation, lymphokine production, and cytotoxicity, PGE usually acts as a feedback inhibitor of the response. This is also true of macrophage and natural killer cytotoxicity. In some instances PGE is responsible for cellular activation rather than inhibition. This is clearest in the control of humoral immunity, where PGE production is a necessary component in the generation of some type of T suppressor cells. Disturbances in immune function found in several human conditions and diseases have been linked to changes in PGE mediated immunoregulation. Either increased production of PGE or increased sensitivity to PGE results in depressed cellular immunity. Conversely drugs which inhibit PGE production act as stimulants of cellular immune function in vitro and in vivo.

Prostaglandin E synthesis and release by murine macrophages and human monocytes after in vitro treatment with biological response modifiers

Prostaglandins of the E series (PGE), produced by mononuclear phagocytes, have many biological activities and are involved in the regulation of myelopoiesis and of the cytotoxic activities of macrophage (M phi) and natural killer (NK) cells. Since one of the possible effects of biological response modifiers (BRMs) on immune regulation might be modulation of PGE production, resident peritoneal murine M phi (mM phi) and elutriated human blood monocytes (hM) were incubated with BRMs and the supernatants were then assayed for PGE. Control mM phi produced about 4.9 ng PGE/10(5) mM phi over a 24 hr period. Lipopolysaccharide (LPS, 1-5 micrograms/ml), polyinosinic-polycytidylic acid complexed with poly-L-lysine (Poly ICLC, 0.1-10 micrograms/ml) and murine alpha, beta-interferon, (IFN, 10-1000 U/ml) all caused a highly significant increase in PGE-secretion. BM41.332, a 2-cyanoaziridine (25-50 micrograms/ml), was found to be less stimulatory, whereas the pyran copolymer MVE-2 (25-50 micrograms/ml), and Azimexone (25-50 micrograms/ml) had marginal effects on PGE-production. Kinetic studies showed that the plateau of PGE-production by mM phi occurred during the first 24 hr of incubation, and mM phi which were washed after a 24 hr incubation period could not be restimulated to produce more PGE. PGE release by hM was increased after stimulation with LPS, Poly IGLC and BM41.332, whereas human IFNs (alpha and beta) induced a slight decrease in PGE production. As in the murine studies, Azimexone and MVE-2 had no detectable effect. The ability of some BRMs to augment PGE-secretion by mM phi and hM may contribute to their negative effects on host responses, such as suppression of NK cell activity.