Imbalance of uterine innate lymphoid cells is involved in the abnormal pregnancy induced by Toxoplasma gondii infection

https://doi.org/10.1016/j.jri.2021.103312Get rights and content

Highlights

  • The percentages and numbers of uILC2s and uILC3s were decreased but uILC1s were increased in T. gondii-infected mice.

  • uILCs expressed higher levels of IFN-γ and TNF-α but lower levels of IL-5 and IL-17 in T. gondii-infected mice.

  • The expression of IL-12Rβ2 and IL-18Rα by uILCs was increased in T. gondii-infected mice.

  • IL-12 and IL-18 treatment induced the alterations in uILC composition in vitro.

Abstract

Toxoplasma gondii (T. gondii) is a ubiquitous intracellular protozoan parasite that causes adverse pregnancy outcomes. Innate lymphoid cells (ILCs) are critical mediators of mucosal immunity, and have been reported to play an important role in uterine vascular adaptation for successful pregnancy. However, the specific role of ILCs in T. gondii-infection-induced adverse pregnancy outcomes remains elusive. In the present study, we found that T. gondii infection caused the imbalance of uterine ILC cells (uILCs). It was characterized by substantially lower expression of the transcription factor GATA-3 and RORγt and higher expression of T-bet in uILCs. Consistent with the transcription factor changes, uILCs from T. gondii-infected mice produced much less IL-5 and IL-17 and substantially more IFN-γ and TNF-α than did uILCs from uninfected mice. Notably, IL-12, IL-18, and their receptors were increased in the uterus of T. gondii-infected mice. In vitro experiments showed that IL-12 and IL-18 treatment reduced the percentages of uILC2 and uILC3 and increased the percentages of uILC1. Conclusion, our data suggest that alterations in uILC composition may disrupt the balance of immune microenvironment after T. gondii infection and contribute to the adverse pregnancy outcomes caused by T. gondii infection.

Introduction

Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite that can infect humans and other warm-blooded animals (Deng et al., 2018; Olariu et al., 2011). T. gondii infection during pregnancy could cause adverse pregnancy outcomes such as embryonic death, resorption, fetal death, abortion, and stillbirth (Fallahi et al., 2018; Kaye, 2011). However, the mechanism of abortion and fetal death remains unknown.

The immune microenvironment at the maternal-fetal interface is closely associated with the maintenance of successful pregnancy (Miller et al., 2018; Tong and Abrahams, 2020). Within the maternal-fetal immune system, decidual NK cells were the largest population of decidual leukocytes during the first trimester (Sojka et al., 2019). NK cells are essential for controlling immune tolerance, trophoblast invasion, vascular remodeling, and fetal-placental growth (Hanna et al., 2006, Sojka et al., 2014). Trained decidual NK cells expressing high levels of IFN-γ and VEGFα, remember the first pregnancy and better assist future gestation (Gamliel et al., 2018).

Besides NK cells, other innate lymphoid cells (ILCs) have also been identified in both human and mouse uterus (Vazquez et al., 2019; Doisne et al., 2015; Vacca et al., 2015). ILCs can be divided into three subgroups based on transcription factors and cytokine production. Group 1 ILCs (ILC1 cells) constitutively express T-bet and are able to produce IFN-γ upon activation (Cording et al., 2016; Klose et al., 2014). Murine uterine ILC1 cells include tissue-resident NK (trNK) cells (Eomes+CD49a+), classical natural killer (cNK) cells (Eomes+CD49a), and helper ILC1 cells (EomesCD49a+) (Sojka et al., 2019; Doisne et al., 2015; Montaldo et al., 2015). Group 2 ILCs (ILC2 cells) constitutively express GATA-3 and produce IL-5 and IL-13 (Krabbendam et al., 2018). Group 3 ILCs (ILC3 cells) express RORγt and produce IL-17 and IL-22 (Klose et al., 2014; Juelke and Romagnani, 2016). Our previous and other studies showed that uterine ILCs (uILCs), especially ILC2 cells increased significantly during pregnancy and played an important role in uterine vascular adaptation for successful pregnancy (Li et al., 2017; Boulenouar et al., 2016). However, the role of uILCs in T. gondii-induced pregnancy failure is not clear.

In this study, using the model of pregnancy failure caused by T. gondii infection, we found that the proportions and numbers of uILC2 and uILC3 were decreased whereas the proportion and number of uILC1 were increased in T. gondii-infected mice. It is worth noting that, IL-12, IL-18, IL-12Rβ2, and IL-18Rα were increased in T. gondii-infected mice. In vitro experiments confirmed that IL-12 and IL-18 induced the imbalance of uILCs. Overall, our data revealed the imbalance of uILCs caused by T. gondii infection, which might contribute to the adverse pregnancy induced by T. gondii infection.

Section snippets

Mice and mating

C57BL/6 mice (8–10 weeks old) were purchased from Beijing Vital River Laboratory Animal Technology Co., Ltd. All mice were kept under specific pathogen-free microenvironment. All animal procedures were conducted in accordance with the National Guidelines for Animal Use in Research (China). The protocols for animal experiments were approved by the ethics committee at Anhui Medical University. All mice were housed (four mice/cage) at 25℃-26℃ on a 12 h light dark cycle, with free access to water

Altered ILC composition in the uteri of T. gondii-infected pregnancy mice

As previously reported, T. gondii infection caused adverse pregnancy in pregnant mice (Fig. S1A–C). To examine the role of uILCs in T. gondii-induced adverse pregnancy, we determined uILCs at gd9.5 (mid-gestation) after T. gondii infection. We used enzymatic protocol to isolate uterine MNCs, and we confirmed that Collagenase IV digestion did not cause CD3 shedding (Fig. S2A–C). Our results showed that the percentage and number of CD45+CD3CD19CD11bLy6G/CThy1.2+ ILCs in the uteri were

Discussion

The immune microenvironment at the maternal-fetal interface is crucial to maintain successful pregnancy (Tong and Abrahams, 2020; Zhang and Sun, 2020). T. gondii infection is known to lead abnormal pregnancy by disrupting the immune balance at the maternal-fetal interface (Piao et al., 2018; Zhao et al., 2017). Our previous study showed that uterine ILCs play an important role in uterine vascular adaptation for successful pregnancy (Li et al., 2017). However, the role of uILCs in T. gondii

Declaration of Competing Interest

The authors report no declarations of interest.

Acknowledgement

This work was supported by the National Natural Science Foundation of China(#81870410).

References (42)

  • S. Aschkenazi et al.

    Differential regulation and function of the Fas/Fas ligand system in human trophoblast cells

    Biol. Reprod.

    (2002)
  • S.M. Bal et al.

    IL-1beta, IL-4 and IL-12 control the fate of group 2 innate lymphoid cells in human airway inflammation in the lungs

    Nat. Immunol.

    (2016)
  • J.H. Bernink et al.

    Human type 1 innate lymphoid cells accumulate in inflamed mucosal tissues

    Nat. Immunol.

    (2013)
  • S. Boulenouar et al.

    The residual innate lymphoid cells in NFIL3-deficient mice support suboptimal maternal adaptations to pregnancy

    Front. Immunol.

    (2016)
  • G. Chaouat et al.

    Tolerance to the foetal allograft?

    Am. J. Reprod. Immunol.

    (2010)
  • S. Cording et al.

    Innate lymphoid cells in defense, immunopathology and immunotherapy

    Nat. Immunol.

    (2016)
  • H. Deng et al.

    Seroprevalence of Toxoplasma gondii in pregnant women and livestock in the mainland of China: a systematic review and hierarchical meta-analysis

    Sci. Rep.

    (2018)
  • J.M. Doisne et al.

    Composition, development, and function of uterine innate lymphoid cells

    J. Immunol.

    (2015)
  • M. Gamliel et al.

    Trained memory of human uterine NK cells enhances their function in subsequent pregnancies

    Immunity

    (2018)
  • Y. Gao et al.

    Tumor immunoevasion by the conversion of effector NK cells into type 1 innate lymphoid cells

    Nat. Immunol.

    (2017)
  • G. Gasteiger et al.

    Tissue residency of innate lymphoid cells in lymphoid and nonlymphoid organs

    Science

    (2015)
  • Cited by (4)

    View full text