The immune response during the luteal phase of the ovarian cycle: increasing sensitivity of human monocytes to endotoxin

Objective: To test the hypothesis that during the luteal phase of the human ovarian cycle, as compared with the follicular phase, the percentage of cy tokines producing peripheral monocytes after in vitro stimulation with endo toxin is increased. Design: Prospective study. Setting: Academic research institution. Patient(s): Women with regular menstrual cycles. Intervention(s): Blood samples were collected between days 6 and 9 of the m enstrual cycle (follicular phase) and between days 6 and 9 of the menstrual cycle following the LH surge (luteal phase). Main Outcome Measure(s): Percentages of tumor necrosis factor (TNF)-alpha-, interleukin (IL)-1 beta-, and IL-12-producing monocytes as well as total w hite blood cell (WBC) count, differential WBC counts, and plasma 17 beta -e stradiol and progesterone concentrations. Result(s): Mean plasma 17 beta -estradiol and progesterone concentrations, percentage of TNF-alpha- and producing monocytes, WBC counts, and granulocy te cell count were significantly increased in the luteal phase as compared with the follicular phase of the ovarian cycle. The percentage of IL-12-pro ducing monocytes, monocyte count and lymphocyte count did not vary between the 2 phases of the ovarian cycle. Conclusion(s): Together with an increase in progesterone and 17 beta -estra diol during the luteal phase, there is an increase in percentage TNF-alpha- and IL-1 beta -producing peripheral monocytes after in vitro stimulation w ith endotoxin as compared with the follicular phase of the ovarian cycle. W hether this increased sensitivity of monocytes for proinflammatory stimuli during the luteal phase is due to increased plasma levels of progesterone o r 17 beta -estradiol needs further investigation. (Fertil Steril(R) 2001;76 :555-9. (C) 2001 by American Society for Reproductive Medicine).