Functional alterations of murine peritoneal macrophages during pregnancy.

We have studied some functional characteristics of murine peritoneal macrophages (MOp) related to hormonal changes produced during pregnancy. Maximal expression of Ia antigen and release of interleukin 1 (IL1) were observed during the first week of pregnancy (implantation), when the highest peak of estradiol was produced. Both Ia antigen expression and IL1 levels progressively decreased as gestation advanced. Inversely, MOp capability to phagocyte and reduce nitro blue tetrazolium (NBT) was diminished at the beginning of pregnancy but returned to normal values in the last week. Sexual steroid levels (estradiol and progesterone) were inversely related, and the release of prostaglandin E2 (PGE2) by MOp decreased when progesterone levels increased. Although PGE2 production had no evident relation with Ia antigen expression and IL1 activity during the first and second weeks of pregnancy, the increment in PGE2 values and percentages of NBT+ cells could indicate a different stage of macrophage activation. These results suggest a possible hormonal regulation of macrophage functionality.