CD56-Positive NK Cells and CD138-Positive Plasma Cells in Basal Decidua of Term Placentas in Singleton Pregnancies After Assisted Reproductive Technology Treatment of Endometriosis-Related Infertility

A eutopic endometrium in endometriosis shows altered immune responses, including abnormalities of NK cells and expression of plasma cells, related to reproductive issues. This study investigated the counts of CD56-positive NK cells and CD138-positive plasma cells in the basal decidua of term placentas in singleton pregnancies after endometriosis-related infertility conceived by assisted reproductive technology (ART). This single-center, case-control study involved immunohistochemical analysis of CD56-positive NK cells and CD138-positive plasma cells in basal decidua using primary monoclonal mouse antibodies, followed by secondary antibodies using a standardized protocol. CD56 and CD138 immunohistochemically positive cells were reported as the total cell count for each studied antibody expressed per 1 mm² of basal decidua (Olympus BX46 and Olympus Image Analyzer). Placental samples containing basal decidua from 36 participants with endometriosis-related infertility who conceived by ART, 31 participants with male factor infertility who conceived by ART and 40 healthy controls were included. Endometriosis decidua showed the lowest median count of CD56-positive NK cells (11.5 / mm², <i>p</i> = 0.039) in BD compared to male factor group (25 / mm²) and healthy controls (24.5 / mm²). No differences were found for CD138-positive plasma cells counts between study groups. Basal decidua in pregnancies after endometriosis-related infertility showed reduced total count of CD56-positive NK cells, without differences in the CD138-positive plasma cell counts compared to control groups. Future studies should investigate how changes in NK cells throughout pregnancy affect the development of perinatal complications and placental pathologies in women with endometriosis, which could uncover potential diagnostic and therapeutic targets.