Chorionic gonadotropin can enhance innate immunity by stimulating macrophage function

Human chorionic gonadotropin (hCG) is a placental glycoprotein, mainly secreted by trophoblasts during pregnancy. Its function in endocrine regulation has been well documented, but its immunological role is still largely unclear. For a successful pregnancy, an effective innate immunity is needed to protect the mother and fetus against infection, while maintaining tolerance against the paternal antigens of the fetus. The aim of this study was to investigate the effect of hCG on the function of macrophages (M phi), which are major players in the innate response. hCG treatment of IFN-gamma-primed M phi resulted in increased production of NO, reactive oxygen species, IL-6 and IL-12p40, and enhanced phagocytosis of apoptotic cells. hCG treatment did not affect the induction of allogeneic T cell proliferation by IFN-gamma-primed M phi. The observed effects were receptor-mediated and involved the protein kinase A signaling pathway, as indicated by blocking studies using specific inhibitors. In vivo thioglycollate-elicited M phi also exhibited increased phagocytic ability upon IFN-gamma activation and hCG treatment. In conclusion, hCG enhances M phi functions involved in innate immunity, while the capacity to stimulate allogeneic T cells remains unchanged.