Inflammation and pregnancy: the role of the immune system at the implantation site

Abstract

The concept that pregnancy is associated with immune suppression has created a myth of pregnancy as a state of immunological weakness and, therefore, of increased susceptibility to infectious diseases. A challenging question is whether the maternal immune system is a friend or a foe of pregnancy. In this review, we discuss data associated to the role of the immune system during pregnancy. We propose a new paradigm in terms of the fetal-maternal immune interaction as well as the immunological response of the mother to microorganism. Our challenge is to better understand the immunology of pregnancy in order to deliver the appropriate treatment to patients with pregnancy complications as well as to determine public policies for the protection of pregnant women during pandemics.

Figure 1. Trophoblast immune interactions

Three stages of interaction. Recruitment :1) Trophoblast sends signals to recruit immune cells towards the implantation site. 2) Education: trophoblast influence the differentiation of immune cells. 3) Response: factors produced by trophoblast-educated immune cells support placental formation and function.

Figure 2. Recruitment of monocytes towards trophoblast cells

In vitro model for the study of trophoblast-immune interactions [33]. A. trophoblast cells form villi-like structures in Matrigel as previously described [33]. B. Monocytes are plated in the top of Matrigel and their movement monitored by in vivo imaging. Note monocyte/macrophage migration from the top of the gel towards trophoblast cells (Bottom). C. Monocyte/macrophage distribution is observed around trophoblast villi-like structures. D. In the absence of trophoblast cells, monocytes/macrophage accumulates in the top of the gel.

Figure 3. Immunologic phases of pregnancy

Each stage of pregnancy is characterized by a unique inflammatory environment. The first and third trimesters are proinflammatory (TH1), whereas the second trimester represents an anti-inflammatory phase also knowns and TH2 environment.