Fetal membranes exhibit selective leukocyte chemotaxic activity during human labor

One of the characteristics of the labor process in women is leukocyte recruitment into reproductive tissues. These migrating cells may play a role in the induction of functional and biochemical changes associated with the rupture of fetal membranes during labor. This study was undertaken to assess whether human fetal membranes induce leukocyte chemotaxis during labor as well as to identify and characterize leukocyte chemoattractants secreted by these tissues. Leukocyte chemotactic activity of fetal membrane extracts obtained from women with full-term pregnancies and spontaneous active labor was compared with extracts from women without labor. The number and phenotype of attracted leukocytes were analyzed by flow cytometry. Chemokines were quantified using a Multiplex system and were identified by immunofluorescence histochemistry. Although all tested extracts induced chemotaxis of leukocytes, those prepared from women undergoing labor induced higher responses. Polymorphonuclear leukocyte chemotaxis increased approximately three-fold in response to extract from fetal membranes with labor. The same extracts elicited a significant increase in attracted monocytes (36-fold) as well as T and B lymphocytes, and NK cells (all five-fold) when compared to extracts from women without labor. This enhanced chemotactic activity was associated with the presence of IL-8, MCP-1, IP-10 and MIP-1alpha. We conclude that fetal membrane extracts obtained from women during labor exhibit selective chemotaxis for specific leukocyte subpopulations in vitro. This process may contribute to a microenvironment composed of specific leukocytes that promotes and amplifies biochemical changes in the fetal membranes during labor.