Effects of prostaglandin F2α and progesterone on the ability of bovine luteal cells to stimulate T lymphocyte proliferation

Bovine luteal cells express class I and 11 major histocompatibility complex molecules and stimulate T lymphocyte proliferation in vitro. Proliferation of T lymphocytes is greater in cocultures of luteal cells and T lymphocytes collected following administration of a luteolytic dose of prostaglandin (PG) F-2alpha. to the cow. Whether this results from changes in luteal cells that increase their ability to stimulate T lymphocyte proliferation or from changes in T lymphocytes that enhance their ability to respond to luteal cells is unclear. To determine which is the case, luteal cell-T lymphocyte cocultures were performed using luteal cells and T lymphocytes isolated from the same animals before and 8 h after administration of PGF(2alpha). In the presence of T lymphocytes collected before PGF(2alpha). administration, luteal cells isolated after PGF(2alpha) were more potent stimulators of T lymphocyte proliferation than were luteal cells collected before PGF(2alpha) (P < 0.05). The effect of progesterone on luteal cell-stimulated T lymphocyte proliferation was also evaluated. Proliferation of T lymphocytes was greater (P < 0.05) in cultures containing the cytochrome P450 side-chain cleavage enzyme-inhibitor aminoglutethimide. Exogenous progesterone caused a dose-dependent inhibition of luteal cell-stimulated T lymphocyte proliferation (P < 0.05). Progesterone-receptor mRNA was undetectable in peripheral blood mononuclear cells collected before and after PGF(2alpha). administration, indicating that the effect of progesterone was not mediated via progesterone receptors in lymphocytes. These results imply that specific changes in luteal cells in response to PGF(2alpha), enhance the ability of these cells to stimulate T lymphocyte proliferation. These results also demonstrate that progesterone can suppress luteal cell-stimulated T lymphocyte proliferation.