Murine peritoneal macrophages in syngeneic and allogeneic pregnancies

We have previously observed that some functional characteristics of peritoneal macrophages (MOp) are altered during syngeneic murine pregnancy. To determine if these alterations are related to the immunological stimulation that the embryo produces on the mother, we evaluated MOp activity in allogeneic pregnancy. We also compared expression of the la antigen, ability to phagocyte and reduce nitro blue tetrazolium (NBT) and to produce interleukin-1 (IL-1) in allogeneic and syngeneic pregnancies. We observed that at Day 7 of pregnancy the increment in MOpIa(+) percentages was more evident in allogeneic (P < 0.05) than syngeneic pregnancies, and that these values remained high during the second week of gestation. We also observed a significant decrease in the macrophages that reduced NAT during the first week both in allogeneic and syngeneic pregnancies. Yet, in the former, the percentages of MOpNBT(+) were still low in the last week of pregnancy (P < 0.05). No differences were found in IL-1 production or in estradiol and progesterone levels between the 2 types of pregnancies. Thus, it is possible to postulate that during the first week of pregnancy the strong antigenic challenge that the embryo represents may activate MOp and that this activation could be augmented when major antigenic differences between mother and embryo are present.