Physiological changes of Fas expression in peripheral lymphocyte subsets during the menstrual cycle

We have examined changes in peripheral lymphocyte subsets, and Fas expression in these subsets, during the menstrual cycle. Measurements were made by three-color flow cytometry in the follicular and luteal phases of the menstrual cycle in ten healthy women. The numbers of leukocytes, granulocytes and monocytes were significantly higher in the luteal phase than the follicular phase. The percentage of CD8⁺ cells was greater in the luteal phase than the follicular phase. The percentages of Fas⁺ cells among T cells and NK cells were higher in the luteal phase than the follicular phase. These findings suggest that the menstrual cycle affects leukocytes, lymphocyte subsets, and Fas expression in these subsets, and that changes in the luteal phase of the menstrual cycle are similar to those in pregnancy.