Unusual inflammation in gynecologic pathology associated with defective endometrial receptivity.

Human cycling endometrium displays a series of periodic transitions unique to this mucosal tissue, which includes rapid proliferation, secretory transformation, physiological angiogenesis, interstitial edema, and menstrual shedding. Among these properties of the endometrium are the inflammatory changes that occur dynamically across the menstrual cycle. Immunocompetent cell composition and inflammatory gene expression pattern in the human endometrium drastically fluctuate from the proliferative phase to the secretory phase, particularly at the time of ovulation. These local immune responses are fine-tuned by the direct or indirect action of two representative ovarian steroids, estradiol and progesterone, and are essential for successful blastocyst implantation. Meanwhile, studies have been accumulating the evidence that such physiological endometrial inflammatory status is altered in the presence of certain gynecologic pathologies. Given that blastocysts are semi-allografts for maternal tissue, even subtle alterations in endometrial immunity potentially have a negative impact on implantation process. In this article, we aimed to review and discuss the physiological and pathological mucosal inflammatory conditions that can affect endometrial receptivity.