The expression of interleukin-15 and interleukin-18 by human term placenta is not affected by lipopolysaccharide

The aim of the study was to examine the stimulatory effect of the inflammatory agent lipopolysaccharide (LPS) on the capacity of human term placenta to secrete interleukin (IL)-15 and IL-18. Isolated placental cotyledons from normal human term deliveries were dually perfused for ten hours with perfusion medium alone (n=5) or with perfusion medium containing LPS (1 microg/kg perfused placental tissue) (n=5). Placental tissue was collected from three different placental compartments (amnion, chorion, and placenta) before and after perfusion. The placental tissues collected were homogenized and examined for IL-15 and IL-18 by ELISA. In addition, formalin-fixed and paraffin-embedded sections from term placentas before perfusion were stained by immunohistochemistry to characterize the cellular origin of placental IL-15 and IL-18. Statistical significance was determined using paired/unpaired t-test. p<0.05 was considered significant. Our results show that IL-15 and IL-18 are produced more by chorionic tissue, as compared to the amnion and placental tissues. Moreover, we show that IL-15 and IL-18 are expressed by epithelial cells of the amnion, chorionic cells of the chorion and decidual cells of the decidua. However, IL-15, but not IL-18, was expressed also by syncytiotrophoblasts of the villi. Perfusion of LPS did not affect the capacity of amnion, chorion and placental tissues to secrete IL-15 and IL-18, as compared to control. The expression of IL-15 and IL-18 in the different compartments of the human placenta suggests a possible role for these two cytokines in normal placental development, pregnancy and labor. Moreover, our results indicate that IL-15 and IL-18 are not part of the mechanism of the response of human placenta to LPS.