Macrophages are a source of IL-17 in the human placenta

To determine if placental macrophages (Hofbauer cells) can synthesize and secrete cytokines of the IL-17 family throughout pregnancy and to reveal the patterns of cytokine expression in early and late gestation.

Macrophages were isolated from the first-trimester and term placental villous tissues from normal pregnancies. Basal and stimulated intracellular production of IL-17A, IL-17E, IL-17F as well as IL-17A secretion was quantified by flow cytometry and cytometric bead array, respectively. The expression of IL-17 and IL-23 receptors was determined on the surface of the placental macrophages by flow cytometry after antibody staining.

In early and late gestation, a substantial proportion of the placental macrophages synthesized IL-17A and IL-17F, but not IL-17E, as determined by intracellular staining of the cytokines. Neither the intracellular production nor the secretion of IL-17 was significantly affected by LPS stimulation and spontaneous labour. The level of secretion decreased slightly but significantly at term. The IL-23 receptor was absent on the surface of cells, whereas variable expression of the IL-17 receptor was observed.

Placental macrophages constitutively produced IL-17 at different gestational ages and represent thus a source of this cytokine in the human placenta. Patterns of the cytokine and receptor expression suggest that this cell population may participate in non-immune processes and contribute to the regulation of placental development and function.