Increased PGE2 from human monocytes isolated in the luteal phase of the menstrual cycle. Implications for immunity?

The reproductive hormones are implicated in the well documented sexual dimorphism in cellular and immune responses. Prostaglandins (PGs) are mediators of the immune response with their concentration and relative amounts being pivotal to their impact. In resident peritoneal macrophages isolated from mice we had previously noted that the cells from females synthesized significantly more PG than males. In these experiments we investigated whether PG metabolism in the human monocyte was influenced by gender and by stage of the menstrual cycle. Monocytes isolated from the female and activated in vitro with LPS produced on average significantly more PG into the medium than the males. Among females, significantly more PG was found in the medium from cells isolated during the luteal phase of the cycle than during the early follicular phase. It was also in this luteal phase in which the female differed substantially from males. We suggest that the in vivo hormonal changes associated with the menstrual cycle modulate monocyte synthesis of PG and other immune modulators such as IL-1. This could be a key to understanding differences in vulnerability between males and females as well as within phases of the cycle, to immune and inflammatory insult.