Modulation of bovine luteal cell synthetic capacity by interferon-gamma

Previous work from our laboratory has demonstrated that major histocompatibility complex (MHC) antigens are expressed on cultured bovine luteal cells following exposure to the T lymphocyte-derived cytokine, interferon-gamma (IFN-γ). In light of these actions of IFN-γ, it was of interest to investigate the effects of this cytokine on other aspects of luteal function. Therefore, bovine luteal cells were cultured for 7 days in the presence or absence of IFN-γ, and luteal progesterone (P₄), prostaglandin F(2α) (PGF(2α)), and 6-keto-prostaglandin F(1α) (6-keto-PGF(1α)) production were evaluated. After a 24-h exposure to IFN-γ (100 U), both PGF(2α) and 6-keto-PGF(1α) production were decreased approximately 50% (p < 0.05). However, as time in culture progressed, IFN-γ markedly increased the synthesis of both prostaglandins approximately 400% above controls (p < 0.05). Stimulation of prostaglandin production by IFN-γ was abrogated by the addition of exogenous P₄. During the period of IFN-γ-stimulated prostaglandin synthesis, LH-stimulated P₄ production was inhibited by IFN-γ treatment. However, the suppression of P₄ production by IFN-γ was not mediated by the increase in prostaglandins since concomitant treatment with indomethacin did not reverse the inhibition of steroidogenesis. These results suggest that IFN-γ, in addition to an indirect role in promoting immune response mechanisms, may also directly affect luteal function by enhancing luteal prostaglandin synthesis and by inhibiting luteal steroidogenesis.