Background:
Monocytes, after neutrophils, are the most abundant white blood cells found in the amniotic cavity of women with intra-amniotic inflammation/infection. However, the origin of such cells has not been fully investigated. Herein, we determined: 1) the origin of amniotic fluid monocytes/macrophages from women with intra-amniotic inflammation/infection, 2) the relationship between the origin of amniotic fluid monocytes/macrophages and preterm or term delivery and 3) the localization of monocytes/macrophages in the placental tissues.
Methods:
Amniotic fluid samples (n=16) were collected from women with suspected intra-amniotic inflammation and/or infection. Amniotic fluid monocytes/macrophages were purified by fluorescence-activated cell sorting and DNA fingerprinting was performed. Blinded placental histopathological evaluations were conducted. Immunohistochemistry was performed to detect CD14+ monocytes/macrophages in the placental tissues.
Results:
DNA fingerprinting revealed that 1) 56.25% (9/16) of amniotic fluid samples had mostly fetal monocytes/macrophages, 2) 37.5% (6/16) had predominantly maternal monocytes/macrophages, and 3) one sample [6.25% (1/16)] had a mixture of fetal and maternal monocytes/macrophages. 4) Most samples with predominantly fetal monocytes/macrophages were from women who delivered early preterm neonates [77.8% (7/9)], whereas all samples with predominately maternal monocytes/macrophages or a mixture of both were from women who delivered term or late preterm neonates [100% (7/7)]. 5) Most of the women included in this study presented acute maternal and fetal inflammatory responses in the placenta [85.7% (12/14)]; and 6) women who had mostly fetal monocytes/macrophages in amniotic fluid had abundant CD14+ cells in the umbilical cord and chorionic plate, whereas women with mostly maternal amniotic fluid monocytes/macrophages had abundant CD14+ cells in the chorioamniotic membranes.
Conclusion:
Amniotic fluid monocytes/macrophages can either be of fetal or maternal origin, or a mixture of both, in women with intra-amniotic inflammation and/or infection. These immune cells could be derived from the fetal and maternal vasculature of the placenta.
Keywords: Acute chorioamnionitis, Clinical chorioamnionitis, Fetal inflammatory response, Funisitis, Innate immune cells, Interleukin-6, Labor, Microbial invasion of the amniotic cavity, Pregnancy, Preterm labor, Term labor