A novel 2B4 receptor leads to worse pregnancy outcomes by facilitating TNF-α and IFN-γ production in dNK cells during Toxoplasma gondii infection

Abstract

Background Infections are a major threat to human reproductive health because they can induce pregnancy failure, including recurrent abortion, stillbirth, and preterm birth. Toxoplasma gondii (T. gondii) infection can result in adverse pregnancy outcomes by affecting certain immune molecules and cytokines. However, the detailed mechanisms behind T. gondii-induced pregnancy failure are poorly understood. Methods Toxoplasma gondii-infected wild-type (WT) pregnant mice and 2B4 knockout (2B4−/−) pregnant mice were established for in vivo study. Human decidual natural killer (dNK) cells were cultured for in vitro study. Abnormal pregnancy outcomes were observed, and the expression of 2B4, functional molecules (CD69, CD107a, tumor necrosis factor alpha [TNF-α], interferon gamma [IFN-γ]), and signaling molecules (SHP-2, Fyn, p-ERK, p-P38) in dNK cells were detected by flow cytometry, Western blot, reverse transcriptase polymerase chain reaction (RT-PCR), and/or immunofluorescence. The direct interactions (2B4 interacts with SHP-2 and Fyn; SHP-2 interacts with p-P38 and 2B4; Fyn interacts with p-ERK and 2B4) were verified by co-immunoprecipitation (co-IP) in NK-92 cells. Results Here, results showed that 2B4 was significantly downregulated after T. gondii infection. Subsequently, infected 2B4−/− pregnant mice displayed worse pregnancy outcomes compared with infected WT pregnant mice. Also, increased TNF-α and IFN-γ expression and elevated dNK cell cytotoxicity were found in 2B4−/− pregnant mice during T. gondii infection. In contrast, reduced TNF-α and IFN-γ expression and decreased human dNK cell activity were found following 2B4 activation during T. gondii infection. Interestingly, results showed that 2B4 binds to adaptor SHP-2 or Fyn, which then triggers different signaling pathways to regulate TNF-α and IFN-γ expression in dNK cells during T. gondii infection. Further, SHP-2 binds 2B4 and p-P38 directly after 2B4 activation, which generates an inhibitory signal for TNF-α and IFN-γ in NK-92 cells. In addition, Fyn can bind to 2B4 and p-ERK after activation of 2B4, thereby inhibiting TNF-α and IFN-γ expression in NK-92 cells following T. gondii infection. Conclusions These data suggest that 2B4 may be a novel danger-signaling molecule that is implicated in pregnancy failure during T. gondii infection. Unraveling the mechanism by which 2B4 regulates dNK cell activity will provide novel insights to aid our understanding of T. gondii-induced adverse pregnancy outcomes. Graphical Abstract

The role of microRNA-142a in Toxoplasma gondii infection-induced downregulation of Foxp3: implications for adverse pregnancy outcomes

“…T. gondii can be transmitted directly to the fetus through the placenta resulting in neonatal miscarriages and fetal malformations [ 30 ]. In the present study, the pregnant mice were injected intraperitoneally at E8.5 with T. gondii .…”

The imbalance in the relationship between inflammatory and regulatory cytokines during gestational toxoplasmosis can be harmful to fetuses: A systematic review

“…This syndrome caused by T. gondii is responsible for the systemic activation of the fetal and maternal immune system ( 42 ). Distinct biomarkers work in a Th1/Th2/Th17 balance thought cytokines (IFN-g, TNF, TGF-beta, IL-1beta, Il-10, IL-12, IL-17, IL-18, IL-22, IL-33, etc), chemokines/receptors (CCL2, CCL22, CXCL1, CXCL2, CXCR3, etc), as well as by Toll-like receptors, nucleotide-binding oligomerization domain-like receptors, and inflammasomes (eg.NLRP3, NLRP5 and NAIP1), defining the pathogenesis behind T. gondii infection during pregnancy ( 19 , 24 , 25 , 27 , 35 , 38 , 46 – 48 ). Beyond this, it is also remarkable to highlight the importance of the genetic variability of T. gondii identified in different continents/countries and, how variability can dictate the prognostic of gestation ( 30 – 32 ) .…”

“…The hallmark behind these studies is the conception that distinct and atypical genotypes dictate the transmissibility and pathogenicity ( 31 , 32 ). In this context, a particular attention must be given to those cases where the maternal protection can be breached during pregnancy, in human or in experimental models, due to different genotypes ( 33 , 34 ) or due to the immune molecular compounds ( 35 ).…”

LILRB4 regulates the function of decidual MDSCs via the SHP-2/STAT6 pathway during Toxoplasma gondii infection

“…Toxoplasma gondii is one of the TORCH pathogens, and its infection could cause the occurrence of abnormal outcomes during pregnancy, such as spontaneous abortion, congenital retinal disease and fetal intrauterine growth retardation [ 45 ]. Our previous studies have shown that T. gondii infection resulted in the dysfunction of several decidual immune cells, such as Mφ [ 27 ], NK cells [ 8 ] and DCs [ 46 ]; however, it remains unknown whether T. gondii infection can result in the dysfunction of dMDSCs. dMDSCs have emerged as one of the novel immuno-modulators for the maintenance of maternal–fetal immune tolerance [ 47 ].…”