Now, researchers comparing pregnancy in opossums and several other mammals have shown how precise control of an immune process, inflammation, is critical to success or failure.
Beyond solving a key mystery about pregnancy, the work could also point to treatments for infertility and miscarriage, says Tom Stewart, an evolutionary developmental biologist at the University of Chicago in Illinois.
This seeming paradox is even more perplexing because although a mother’s inflammatory reaction to this “Parasite” is the biggest threat to pregnancy, it also seems necessary for the pregnancy to be successful, Wagner, Chavan, and Yale postdoc Oliver Griffith pointed out last year.
After about 2 days, the mother’s immune system “Rejects” the embryos, causing the birth of a litter still at a very immature developmental stage compared with placental mammals.
The genes revealed the array of immune system signaling molecules and steroid hormones taking part in the immune attack on the embryo.
The gene activity also pointed to a role for immune cells such as neutrophils, which launch a full-fledged inflammatory reaction, including the release of molecules that stimulate contractions of the uterus.
Based on studies of gene activity and immune cells, he found that these mammals have “Domesticated” implantation’s inflammatory response.