Dendritic Cells And Uterine NK Cells Interaction Contributed To Abnormal Pregnancy With Toxoplasma Gondii Infection

Objective:To investigate the cross-talk between uNKs and DCs with T. gondii infection to infer the mechanism that results in abnormal pregnancy outcomes. Methods:Purified uNKs from normal pregnant and DCs from normal non-pregnant C57BL/6 mice were co-cultured at the ratio of 5:1 in the presence or absence of T. gondii for 24 hr in vitro. Transwell group and direct group were established. Also, pregnant mice infected with T. gondii were established. In vivo 24 pregnant C57BL/6 mice were randomly divided into infection group (12 mice) and control group (12 mice). Infection group mice were inoculated intraperitoneally with 400 tachyzoites on GD 8 and control group mice were inoculated with same dose sterile PBS at the same time. All mice were euthanized on GD 14, placentas and fetuses were observed. IL-12R, inhibitory receptor NKG2A, and activating receptor NKG2D expressed on uNKs were analyzed by flow cytometry. The levels of IL-12 and IFN-y in supernatants and placenta were measured by ELISA. The cytotoxic activity of uNKs was evaluated by flow cytometry. Results:On GD 14, we found that the placentas from infected mice were hemorrhagic when compared to those of uninfected control mice, which had a better blood supply. The stillbirth rate of infected mice was significantly increased compared with that of control mice (p<0.01). IL-12R, NKG2A, and NKG2D were up-regulated following T. gondii infection, but NKG2D was significantly higher than NKG2A. NKG2D and cytotoxicity of uNKs co-cultured were elevated with the increasing of IL-12 upon T. gondii infection compared with uNKs infected alone. In addition, IFN-y in co-cultured supernatants were higher than DCs or uNKs alone, while IFN-y enhancement was largely abrogated when cells were cultured in the presence of anti-IL-12 antibody. Moreover, IL-12 and IFN-y in placenta were also significantly increased in infected mice.Conclusions:Upon T. gondii infection, DCs enhanced activation, cytotoxicity and IFN-γ secretion of uNKs through IL-12 and IL-12R interaction. This interaction was related to abnormal pregnancy outcomes induced by T. gondii infection.