CYCLIC PLASMA IL-6 LEVELS DURING NORMAL MENSTRUAL-CYCLE

Steroid hormones including sex hormones are known to influence cytokin e production by cells in vitro, We investigated whether there art? dif ferences in cytokine production in vivo and ex vivo during the menstru al cycle in five ovulating women compared with five pregnant women and nine males, Interleukin 6 (IL-6) in plasma changed periodically durin g 12 of 13 cycles in five women, The IL-6 levels were lowest in the lu teal phase when progesterone levels mere elevated and highest preovula tory when progesterone levels were low (P < 0.009), This phenomenon wa s unrelated to changes in haematocrit or albumin and independent of co rtisone, growth hormone, luteinizing or follicle stimulating hormone a nd testosterone. In contrast to IL-6, the soluble IL-6 receptor did no t vary significantly during the menstrual cycle. In comparison, nine m ales and five pregnant women had low plasma IL-6 levels comparable wit h women during the luteal phase, In addition, levels of IL-6, IL-10 an d TNF were determined after whole blood stimulation with lipopolysacch aride ex vivo during a menstrual cycle. Neither the number of CD-14(+) or CD14/CD16(+) cells nor the amounts of IL-6, IL-10 and TNF after s timulation showed cyclic changes. We suggest that sea hormones, especi ally oestrogen and progesterone, may influence immune responses by dec reasing basal IL-6 levels in vivo. (C) 1997 Academic Press Limited.