Improvement of LIF release by mononuclear cell cultures by 24 h incubation before stimulation with ConA.

By measuring granulocyte migration from clotted plasma droplets placed in Microtest II plates, leucocyte migration inhibitory factor (LIF) production by concanavalin A (ConA) stimulated mononuclear cell (MNC) cultures was tested. Moderate LIF production was observed when mononuclear cells were pulsed with ConA at 0 h, as compared with cells stimulated after 24 h culture which produced a significantly increased amount of LIF. Fresh adherent cells, when added to 24 h incubated MNC cultures before ConA stimulation, decreased LIF production, in contrast to in vitro irradiated or overnight cultured adherent cells. Indomethacin, when present during exposure to a ConA pulse of either MNC or of adherent cell-rich 24 h incubated MNC cultures, improved LIF activity significantly. This suggests that prostaglandin producing adherent cells, presumably cooperating with radiosensitive short-lived immunoregulatory T cells, are involved in suppression of LIF production by MNC cultures stimulated by ConA at 0 h.