The immune system in pregnancy: a unique complexity

Abstract

Placental immune response and its tropism for specific viruses and pathogens affect the outcome of the pregnant woman's susceptibility to and severity of certain infectious diseases. The generalization of pregnancy as a condition of immune suppression or increased risk is misleading and prevents the determination of adequate guidelines for treating pregnant women during pandemics. There is a need to evaluate the interaction of each specific pathogen with the fetal/placental unit and its responses to design the adequate prophylaxis or therapy. The complexity of the immunology of pregnancy and the focus, for many years, on the concept of immunology of pregnancy as an organ transplantation have complicated the field and delayed the development of new guidelines with clinical implications that could help to answer these and other relevant questions. Our challenge as scientists and clinicians interested in the field of reproductive immunology is to evaluate many of the 'classical concepts' to define new approaches for a better understanding of the immunology of pregnancy that will benefit mothers and fetuses in different clinical scenarios.

Fig. 1

Integrational view of the immune system during pregnancy. a) The old model conceives the maternal immune system as the major player in response to the fetus and microorganisms. Fetal responses (fetus and placenta) are considered limited. b) New integrational model where the fetal–placental immune response and the maternal immune system are integrated. (see text for detail).

Fig. 2

Role of the placenta as a modulator of fetal and maternal responses. Inflammation at the placenta has a bi-directional effect: Activates the maternal immune system as well as the fetus by creating an inflammatory environment. FIRS, Fetal inflammatory response syndrome.