Characterization of Cytokine Production by Human Term Placenta Macrophages In Vitro

Macrophages are apparently the only immune cells within placenta villi, yet functions of these cells remain obscure. It has been postulated that placental macrophages accomplish regulatory roles at the fetal-maternal interface by means of wide variety of secreted cytokines. We attempt to analyze the patterns of cytokine production in an isolated population of placental macrophages. Macrophages were obtained from term placentas in the absence of spontaneous labor. The basal and lipopolysaccharide (LPS)-stimulated levels of intracellular cytokines were detected by flow cytometry. The basal cytokine secretion was determined by BD((TM))Cytometry Bead Array (BD Biosciences, San Diego, CA, USA). Intracellular IL-1 alpha, IL-1 beta, IL-6, and TNF alpha were detected in 31, 27, 4, and 3% CD68+ cells, respectively. Stimulation with LPS increased the proportions of cytokine-producing CD68+ cells to 48, 50, 28, and 49%, respectively. Under basal conditions, levels of released TNF alpha and IL-6, respectively, were 20- and 25-fold higher when compared with IL-1 beta while IL-10 was secreted in small but detectable amounts. When a secretory activity was estimated for cytokine-producing cells, the secretion rate for TNF alpha and IL-6 overwhelmingly surpassed that for IL-1 beta (TNF alpha:IL-6:IL-1 beta ratio was 192:145:1). These results suggest functional heterogeneity of the placental macrophage population and contribute to the elucidation of regulatory roles of these cells in gestation.