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. To discuss this question we will first
review some fundamental concepts associated with Vadimezan datasheet the immune system and pregnancy. A fundamental feature of the immune system is to protect the host from pathogens. This function depends upon the innate immune system’s capacity to coordinate cell migration for surveillance and to recognize and respond to invading microorganisms. During normal pregnancy, the human decidua contains a high number of immune cells, such as macrophages, natural killer (NK) cells and regulatory T cells (Treg).1–3 Seventy percent buy Crenolanib of decidual leukocytes are NK cells, 20–25% are macrophages and 1.7% are dendritic cells.2,4,5 From the adaptive immune system, B cells are absent, but T lymphocytes constitute about 3–10% of the decidual immune cells.6 During the first trimester, NK cells, dendritic cells and macrophages infiltrate the decidua and accumulate around the invading trophoblast cells.7,8 Deletion of either macrophages, NK cells or dendritic cells (DC) has deleterious effects.9–14 Elegant studies have shown that in the absence of NK cells, trophoblast cells are not able
to reach the endometrial vascularity leading to termination of the pregnancy.12 These studies suggest that uNK cells are critical for trophoblast invasion in the uterus. Similarly, depletion of DCs prevented
blastocyst implantation and decidual formation.15 Indeed, this study suggests that uDC are necessary for decidual formation and may affect the angiogenic response by inhibiting blood vessel maturation.15 More recently, Collins et al. demonstrate that uDC association with T cell responses to the fetal ‘allograft’ starkly contrast with their prominent role in organ transplant rejection.16 These data further support the idea that the fetal–maternal immune interaction is more complex than the comparison to transplant allograft. Consequently, the presence of immune cells at the implantation old site is not associated with a response to the ‘foreign’ fetus but to facilitate and protect the pregnancy. Therefore, the immune system at the implantation site is not suppressed, on the contrary it is active, functional and is carefully controlled. Is the systemic immunity of the mother suppressed? Although we can find numerous studies describing the factors inducing immune suppression (including progesterone, defined as the natural immune suppressor), medical and evolutionary aspects are against the concept of immune suppression.