Inflammation and pregnancy: the role of toll-like receptors in trophoblast-immune interaction.

During normal pregnancy, the decidua is populated by a variety of leucocytes; however, cells of the innate immune system seem to dominate this tissue. Their presence suggests that the innate immune system is not indifferent to the fetus and has been associated with a response of the maternal immune system to the "semi-allograft fetus." New evidences, however, indicates that these immune cells are critical for decidual and trophoblast development, rather than induction of tolerance. We hypothesized that, during implantation, an inflammatory environment is necessary for the attachment and invasion of the blastocyst. Therefore, we propose the existence of an "inflammatory-mediated embryo implantation" condition that is dependent on the proper "education" of the innate immune system by the trophoblast. Here we postulate that trophoblast cells successfully orchestrate their inflammatory environment and regulate immune cell differentiation and activation.