Luteal phase of the menstrual cycle in young healthy women is associated with decline in interleukin 2 levels

The aim of this study was to look at the possible changes in the blood leve ls of Interleukin 2 (IL2) during the sexual cycle in generally healthy, you ng, regularly menstruating women. The concentrations of progesterone and 17 beta -estradiol were measured using radioimmunological assay. The bioactiv ity of interleukin 2 was measured using a biological test on the IL2-sensit ive CTLL cell line. The percentage of lymphocytes with intracellular IL2 wa s determined by flow cytometry. Eighteen healthy volunteers (19-29 years ol d) were examined on days 5, 8, 14, 18 and 25 of the same cycle. All women w ere characterised by a regular menstrual cycle as per physiological levels of 17 beta -estradiol and progesterone. The luteal phase of the cycle was c haracterised by both a decrease of IL2 blood levels and a decrease in the p ercentage of intracellular IL2-containing lymphocytes stimulated in vitro. The IL2 level fluctuations observed during the menstrual cycle may be one f actor causing pre-menstrual infections observed in young women. On the othe r hand, the decrease of IL2 may be seen as a start of the immune suppressio n necessary for an embryo's nidation.