Macrophage migration inhibitory factor in the bovine corpus luteum: characterization of steady-state messenger ribonucleic acid and immunohistochemical localization

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine produced by T cells and macrophages. A number of tissues also produce MIF during states of active differentiation and/or proliferation. The purpose o f this study was to determine whether MIF is present in the corpus luteum ( CL). The steady-state mRNA for MIF was examined in CL by Northern analysis on Day 5, Days 9-12, and Day 18 of the estrous cycle and at 0.5, 1, 4, 12, 24, and 36 h after a luteolytic injection of prostaglandin F-2 alpha (PGF(2 alpha)) (n = 4 CL per time point). The greatest amount of MIF mRNA was obs erved in Day 5 CL compared with midcycle and Day 18 CL. Messenger RNA for M IF in CL collected 0.5 h post-PCF2 alpha was greater than in midcycle and a ll other regressing CL. Immunohistochemical analysis (n = 4) revealed that MIF was present in the bovine CL throughout the estrous cycle and appeared to be localized to large luteal cells. It was concluded that MIF is produce d within the bovine CL, mRNA expression is maximal in the early CL, and the protein is primarily localized to large luteal cells. The functional signi ficance of MIF remains to be determined.