Plasmacytoid dendritic cells (pDCs) rapidly produce large amounts of type 1 interferon (IFN) after Toll-like receptor 7 and 9 engagements. This specialized function of type 1 IFN production is directly linked to the constitutive expression of IRF7, the master transcription factor for type 1 IFN production. However, the IRF7 regulatory network in pDCs remains largely unknown. In this study, we identify that the transcription factor NFATC3 specifically binds to IRF7 and enhances IRF7-mediated IFN production. Furthermore, knockout of NFATC3 greatly reduced the CpG DNA-induced nuclear translocation of IRF7, which resulted in impaired type 1 IFN production in vitro and in vivo. In addition, we found that NFATC3 and IRF7 both bound to type 1 IFN promoters and that the NFAT binding site in IFN promoters was required for IRF7-mediated IFN expression. Collectively, our study shows that the transcription factor NFATC3 binds to IRF7 and functions synergistically to enhance IRF7-mediated IFN expression in pDCs.
Intrauterine infection is a major cause of immune imbalance at the maternal-fetal interface, which leads to spontaneous abortion, premature rupture of the fetal membranes, and preterm birth. Human amniotic epithelial cells (hAECs) play a fundamental role in the maintenance of pregnancy. We hypothesize that bacteria influence the immunomodulatory effects of hAECs through stimulation of Toll-like receptors (TLRs). Here, we investigated how lipopolysaccharide (LPS) as a bacterial component affects anti-inflammatory and pro-inflammatory cytokines production of hAECs. Human placentas were obtained from six healthy pregnant women and hAECs were isolated. The phenotypic characteristics of hAECs were determined by flow cytometry. The hAECs (4 × 105 cells/ml) were cultured in the presence or absence of LPS (5 µg/ml). The viability of the cells was assessed and culture supernatants of hAECs were collected after 24, 48 and 72 h of incubation. The levels of transforming growth factor-beta1 (TGF-ß1), interleukin-4 (IL-4), tumor necrosis factor-alpha (TNF-a), interleukin-17 A (IL-17A), and interferon-gamma (IFN-?) were measured by ELISA. Our data showed that LPS treatment did not affect the viability of hAECs, while had a stimulatory effect on TGF-ß1 production of hAECs (p < 0.001). A significant reduction in IL-4 production of LPS-stimulated hAECs was observed (p < 0.05). LPS enhanced the production of TNF-a and IL-17 A of hAECs (p < 0.05-0.0001). The IFN-? level was only detectable in two culture supernatants of hAECs, and the level was unchanged after stimulation with LPS. Based on these findings, LPS may play a pivotal role in immune imbalance at the feto-maternal interface through affecting anti-inflammatory and pro-inflammatory cytokines production of hAECs.
