201. Higher levels of memory T-cell subsets in decidua parietalis compared to basalis tissue of uncomplicated term pregnancies

Introduction During pregnancy, tolerance towards the fetus is induced by adaptations in the maternal immune system. Maladaptation of the maternal immune system is associated with pregnancy complications like preeclampsia and fetal growth restriction. Memory T-cells might play an important role in fetal-maternal tolerance. It is at the fetal-maternal interface where the maternal immune system especially needs to create tolerance towards the fetus. Decidua basalis is the maternal part of the basal plate whereas decidua parietalis is the maternal part of the fetal membranes. Decidual distribution pattern of memory T-cells during pregnancy is not known. Objective Since it is unknown how memory T-cells are distributed in decidual tissue, memory T-cells in decidua basalis and decidua parietalis were evaluated. Methods Lymphocytes were isolated from decidua basalis and decidua parietalis from uncomplicated term pregnancies. Using flowcytometry, subsets of memory T-cells (central, effector, regulatory, and tissue resident) of uncomplicated term pregnancies were analysed (n = 27). To compare different subsets of memory T-cells between decidual tissues, a student’s t-test ( p Results Levels of memory T-cells (CD45RO+) were higher in decidua parietalis compared to decidua basalis in both CD4+ and CD8+ cells. Moreover, CD8+ central memory cells (CD45RO+CCR7+) and CD8+ tissue resident cells (CD45RO+CD103+) were higher in decidua parietalis compared to decidua basalis. Lastly, activation status (CD69+) was higher for all memory subsets (except for CD4+ effector memory T-cells) in decidua parietalis compared to decidua basalis. Discussion This study shows that memory T-cell subsets are differently distributed in decidua parietalis and basalis, with higher percentages of memory T-cell subsets as well as more activated memory T-cell subsets found in decidua parietalis compared to decidua basalis. Since memory T-cells are found to be present at higher percentages in decidua parietalis, this could suggest that these cells are especially important for creating tolerance to the fetal membranes.