Progesterone binding to lymphocytes-cause for transient loss of HLA antigens in women?

In 5 women with normal ovulation cycle the weakening to loss of lymphocyte HLA antigens was proved in most menstrual periods and in the interval between two menstruations, sometimes on days 20-23 of the genital cycle. In the intermenstrual period the increase of the progesterone level in the blood was found. The binding of progesterone on the lymphocyte surface seems to be the cause of the blocking of HLA antigens in the intermenstrual period.