Problem: 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.
Method of study: 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 Cytometry Bead Array (BD Biosciences, San Diego, CA, USA).
Results: Intracellular IL-1alpha, IL-1beta, IL-6, and TNFalpha 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 TNFalpha and IL-6, respectively, were 20- and 25-fold higher when compared with IL-1b while IL-10 was secreted in small but detectable amounts. When a secretory activity was estimated for cytokine-producing cells, the secretion rate for TNFalpha and IL-6 overwhelmingly surpassed that for IL-1beta (TNFalpha:IL-6:IL-1beta ratio was 192:145:1).
Conclusion: These results suggest functional heterogeneity of the placental macrophage population and contribute to the elucidation of regulatory roles of these cells in gestation.