Inflammatory responses of macrophages in the chorioamniotic membranes of the human placenta
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Macrophages, key constituents in innate and adaptive immune responses, display classical (pro inflammatory) and alternative (anti-inflammatory) activation patterns depending on disease stage and stimuli. Given that intraamniotic inflammation and infection complicate one third of preterm labor pregnancies, the objective of this study was to examine the patterns of macrophage activation in the normal and inflamed human fetomatemal interface. Using quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC), we studied the mRNA expression of CD 163 (alternative macrophage activation marker) and CD 14 (classical macrophage activation marker) in the chorioamniotic membranes (n=40) and placentas (n=40) of full-term and preterm labor pregnancies with and without histological chorioamnionitis and funisitis. As expected, CD 163 mRNA expression was significantly higher in uninflamed chorioamniotic membranes of term and preterm labor cases, while CD 14 mRNA expression was higher in inflamed chorioamniotic membranes of preterm labor cases. There was no difference in CD163 or CD14 mRNA expression in placental tissues of the same cases. Immunostaining revealed increased CD 14 immunoreactivity in maternal decidual macrophages. Interestingly, these macrophages did not show significant migratory response whereas neutrophils in the same cases showed extensive migration. Thus, we demonstrated that the macrophages in the chorioamniotic membranes, but not villous placenta, switch their activation pattern with acute chorioamnionitis. Minimal migratory response of classically activated macrophages in the chorioamniotic membranes also suggests a uniqueness of these macrophages at the fetomaternal interface.