The role of interleukin-1 in reproduction.

A series of investigations on the interaction between interleukin-1 (IL-1) and the reproductive system is reported and their implications discussed. IL-1 is a 17-kDa polypeptide made by peripheral monocytes and tissue macrophages known to be involved in various aspects of the inflammatory response such as collagenase PGE2 osteolysis lymphocyte stimulation and release of several other cytokines. IL-1 was released by peripheral monocytes from male volunteers and incubated in vitro in the presence of estradiol and progesterone at physiologic doses. Similarly peripheral monocytes from regularly cycling women synthesized the mRNA for IL-1 in the presence of added estradiol and progesterone in vitro. Increasing doses of progesterone resulted in decreasing amounts of IL-1 mRNA while increasing doses of estradiol gave a biphasic response. The effects were explored of physiologic levels of estradiol and progesterone on secretion of IL-1 by peripheral monocytes taken from women with cycles stimulated by human menopausal gonadotropin/hCG before ovulation in late luteal phase in the midtrimester and in the third trimester of pregnancy. The most dramatic effects on release of IL-1 was in midtrimester when progesterone decreased IL-1 production in 4 of 6 women and progesterone with estradiol decreased IL-1 in 5 of 6 women. In another experiment 4 cell mouse embryos were cultured with IL-1 and IL-2 without adverse effect. The response of IL-1 to gonadal steroids may be implicated in the normal postovulatory and pregnancy temperature increase. This cytokine may also be involved in the process of osteoporosis undergone by postmenopausal women which is reversible by steroids.