Comparison of decidual leukocytes following spontaneous vaginal delivery and elective cesarean section in uncomplicated human term pregnancy.

The aim of this study was to quantify and compare leukocyte populations in term decidua basalis and parietalis obtained after spontaneous vaginal delivery (SVD) or elective cesarean section (CS) without labor. Decidua basalis and parietalis samples were obtained from placentas after SVD (n = 20) and after CS (n = 30). Following mechanical disaggregation, leukocytes were purified and stained with monoclonal antibodies. Percentages of leukocyte subclasses within the CD45(+) cell fraction and activated T cells were determined by flow cytometry. No differences were found in the percentages of CD45(+) cells or CD56(bright)CD16(-) uterine natural killer (NK) cells between decidua basalis from SVD and CS or between decidua parietalis from SVD and CS. In decidua basalis and parietalis from SVD, a significantly higher number of CD56(dim)CD16(+) NK cells was found compared to CS. In decidua basalis from SVD, there was a significantly lower percentage of CD14(+) cells and higher percentage of CD19(+) cells compared to CS. The percentage of CD3(+) T cells expressing CD25 or human leukocyte antigen (HLA)-DR was significantly decreased in decidua basalis and parietalis from SVD compared to CS. Comparison of decidua collected after SVD or CS suggests that labor is associated with dynamic changes in the distribution of decidual leukocytes, specifically NK and T cell subpopulations. In particular, the disappearance of the CD4(+)CD25(+) T cell population, which possibly contains a subpopulation of regulatory T cells, may contribute to the initiation of labor. Further investigation into factors affecting decidual leukocytes may expand our understanding of the immunological events at the maternal-fetal interface.