[Cytokines and the corpus luteum]

This minireview present main findings concerning the contribution of cytokines to the regulation of some key processes of luteal functions. Data concerning the preovulatory follicles invasion by white blood cells and the migration of macrophages, granulocytes and T lymphocytes into corpus luteum suggest that local secretion of regulatory cytokines may be involved in regulating corpus luteum formation and demise as well its maintenance in early pregnancy. Several lines of evidence indicate that the pro-inflammatory cytokines such as IL-1, IL-6 and TNF-alpha modulate the steroidogenic changes which take place during luteinization. For instance, an inhibition of E2 biosynthesis is evidenced in granulosa cells in human or porcine species with IL-1, in rat with TNF-a and in bovine with IL-6. Moreover, IL-1 stimulates P4 production but to a much lower extent than LH, and PGE2 synthesis by rat thecal cells. The potential relevance of pro-inflammatory cytokines in the mechanisms controlling luteolysis is suggested by the ability of IL-1 and TNF-alpha to decrease both P4 production and the survival of bovine luteal cells. As opposed to ruminants, TNF-alpha has no effect in human luteal cells but potentiates the decrease of P4 secretion induced by IFN-gamma. Finally, data regarding the participation of trophoblast interferons in the mechanisms for maintaining the corpus luteum at the establishment of pregnancy are now available in ruminants. From these observations and others, we can consider that cytokines are involved in the regulation of the corpus luteum function.