Luteal leukocytes are modulators of the steroidogenic process of human mid-luteal cells

Flow cytometry analysis of luteal cells revealed that an important proportion of these cells are leukocytes. The percentage of leukocytes was higher in the early (42 +/- 4) and late (35 +/- 3) luteal phases than in the mid-luteal (24 +/- 2) phase. However, the proportion of macrophages did not differ between the luteal stages. The how cytometric properties correlated with cellular size and granularity were not reliable as discriminators of luteal cell subpopulations. Therefore, to assess the contribution of luteal leukocytes, these cells mere completely removed from luteal cell suspensions (total cells), by a negative selection procedure (immunomagnetic separation), The functional role of leukocytes in mid-luteal steroidogenesis was assessed, in total as well as leukocyte-depleted cells. Progesterone production was found to have increased 2.2-fold in leukocyte-depleted cell cultures, in comparison with total cells under basal conditions. However, the response to human chorionic gonadotrophin (HCG) was 36% lower under the latter conditions. Oestradiol production was not significantly modified under basal or HCG-treated conditions. In leukocyte-depleted cells, the concentration of interleukin (IL)-1 beta decreased 5-fold in comparison with total cell cultures, suggesting that leukocytes are the principal source of IL-1 beta, In summary, the results of the present investigation suggest functional interactions between the immune system and steroidogenic cells of the human corpus luteum.