Immune mechanisms at the maternal-fetal interface: perspectives and challenges

Abstract

Leaders gathered at the US National Institutes of Health in November 2014 to discuss recent advances and emerging research areas in aspects of maternal-fetal immunity that may affect fetal development and pregnancy success.

Figure 1

Classification of placentas based on histological assessment of the maternal-chorion interface. (a) Epitheliochorial placenta as seen in cow, pig and sheep: the barrier between maternal blood and the chorion (tan cells) consists of the maternal vascular endothelium and uterine epithelium (blue cells). Red cells are vascular endothelium. (b) Endotheliochorial placenta as observed in dog and cat: the barrier between maternal blood and the chorion consists of the maternal vascular endothelium. (c) Hemochorial placenta as seen in human and small rodents (such as rat and mouse): maternal blood directly bathes the chorionic villi.

Figure 2

Various immune cells interact with uterine and trophoblast cells during pregnancy. (a) Uterine spiral artery remodeling during pregnancy. uNK cells (green cells) surrounding a spiral artery in the mouse. Courtesy of P. Lenhart (University of North Carolina, Chapel Hill). (b) Trophoblast cells (green cells) are replacing the endothelial cells of one spiral artery (bottom) and have completely replaced endothelial cells in the other artery (above) in the rat. Courtesy of D. Chakraborty (University of Kansas Medical Center, Kansas City). (c) Human pregnant uterine immune cells: CD14⁺ decidual macrophages (brown) in close contact with extravillous trophoblast. Sample collected from a third-trimester decidua, cesarean section term not labor.

Figure 3

Tolerance to the semiallogeneic fetus compared with organ transplantation. Fetal tissues expressing paternal antigens during pregnancy and allografts after transplantation are each recognized as immunologically foreign. However, in contrast to transplanted organ allografts, which require exogenous immune suppression to prevent rejection, an increasingly wide variety of local and systemic immunological shifts occur during pregnancy that maintain fetal tolerance and prevent ‘rejection’ of the semiallogeneic fetus.