Expression of cytokine messenger ribonucleic acids in the bovine corpus luteum

There is considerable evidence that luteolysis in the cow and other species involves components of the immune system. In this study, we examined the expression of the mRNAs for TNF-α, IFN-γ, IL-1β, IL-2, and IL-2 receptor (IL-2R) by reverse transcription-polymerase chain reaction (RT-PCR) using bovine-specific primers. Expression was examined in corpora lutea (CL) of the early (day 5), mid (days 11-12), and late (day 18) luteal phase, and at 1, 4, and 24 hours following a luteolytic dose of prostaglandin (PG) F(2α). Tumor necrosis factor-α, IFN-γ, and IL-1β mRNAs were detectable by RT-PCR at all stages of the cycle examined. Densitometric intensities of the electrophoresed IFN-γ PCR products revealed a drop in RNA expression during late diestrus and at one hour of prostaglandin-induced luteolysis (P < 0.05). The mRNA for TNF-α seemed to remain constant during the cycle, and rose slightly during luteolysis. Interleukin-1β mRNA also did not vary during the cycle or during luteolysis. Finally, expression of mRNAs for IL-2 and IL-2 receptor was not evident in CL by the methods employed in this study. These results are the first to describe mRNA expression for TNF-α, IFN-γ, and IL- 1β in the bovine corpus luteum, and support a role for these cytokines in luteal function and regression.