110 Characterizing the immune cell population in the human fetal membrane

Abstract

Fetal membrane (amnion and chorion) inflammation provides one of the mechanistic triggers of human parturition at term. Immunocompetent membrane cells are sources of inflammatory mediators (cytokines/chemokines); however, the role of immune cells contributing to inflammation, either resident or emigrated to the membranes, and their origin (fetal vs. maternal) is unclear. This study determined changes associated with immune cells, their number, and location in human fetal membranes from term not in labor (TNIL) and term labor (TL) samples. Fetal membranes from normal TNIL (N=9) and TL (N=6) samples were analyzed by immunohistochemistry (IHC), immunofluorescence (IF), and flow cytometry for evidence of total (CD45+) immune cells as well as innate immune cells (neutrophils, macrophages and NK cells) using specific markers. Fetal origin of immune cells was determined using polymerase chain reaction (PCR) for the SRY gene in the Y chromosome. Statistical analysis was performed using Student’s t test. Data are presented as mean ± standard error of the mean. CD45+ cells were localized in human fetal membranes in both TNIL and TL. A three-fold increase in CD45+ cells were seen in TL fetal membranes of (7.73% ± 2.35) compared to TNIL (2.38% ± 0.78; P = 0.01). This increase is primarily contributed by an influx of neutrophils (TL 15.38% ± 4.28; TNIL 5.74% ± 1.79; P = 0.02). Macrophages and NK cells did not change in the membranes between TNIL and TL. PCR data determined that leukocytes of fetal origin are present in the fetal membranes. This is the first report to show innate immune cells of fetal origin in the human fetal membranes. There is a moderate increase in the number of immune cells in the fetal membranes of TL; however, it is unclear whether this is a cause or consequence of labor. Further functional studies are needed to determine the functional role for these cells in membrane inflammation.View Large Image Figure ViewerDownload Hi-res image Download (PPT)