Cultured human luteal peripheral monocytes secrete increased levels of interleukin-1

Abstract

Interleukin-1 (IL-1), an immune monokine secreted by activated macrophages and monocytes, appears to be intimately involved in endocrine phenomena. It is well established that IL-1 mediates a number of immune and inflammatory responses. In addition, the production of IL-1 appears to be modulated by the gonadal estradiol and progesterone, leading to this study of IL-1 secretion by cultured peripheral monocytes isolated at varying times during the menstrual cycle and pregnancy. Circulating peripheral monocytes were isolated from eight women undergoing human menopausal gonadotropin-stimulated ovulation induction during the late follicular phase just before hCG administration and from eight similarly stimulated women on the 12th day after hCG administration. Peripheral monocytes were also isolated from six women during both second and third trimester pregnancy. After 48 h in culture, conditioned media were assayed for IL-1 bioactivity using the D1O lymphocyte proliferation assay. Significantly more IL-1 bioactivity was secreted by monocytes isolated in the luteal phase of the cycle (52.4 +/- 17.5 IU/mL) compared to that in late follicular phase (5.2 +/- 0.9 IU/mL; P = 0.001) or third trimester of pregnancy (7.0 +/- 1.5 IU/mL; P = 0.006). Thus, peripheral monocyte IL-1 secretion appears to be increased by luteal levels of progesterone, although further elevation of progesterone during pregnancy returns IL-1 levels to the preovulatory baseline. In addition, basal body temperatures obtained in four women during third trimester pregnancy were 98 F or less. Thus, IL-1 secretion from cultured monocytes appears to increase with luteal concentrations of progesterone and decrease to preovulatory levels at higher concentrations of the steroid during pregnancy, which may account for the dissociation of high progesterone levels and elevated basal body temperature during late pregnancy.