Human placental trophoblast cells contribute to maternal-fetal tolerance through expressing IL-35 and mediating iT<sub>R</sub>35 conversion.

Liu, Jia; Hao, Shengnan; Chen, Xi; Zhao, Hui; Du, Lutao; Ren, Hanxiao; Wang, Chuanxin; Mao, Haiting · Nat Commun · 2019

basic_science · Level V

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Abstract

During pregnancy, trophoblast cells sustain the maternal-fetal tolerance via expressing and secreting various chemokines and cytokines. Our previous study revealed the expression of interleukin-35 (IL-35) in human first-trimester trophoblasts. Here we show that IL-35 is expressed in both human first-trimester primary trophoblast cells and a trophoblast cell line. Trophoblast cells inhibit the proliferation of human naive conventional T cells (T<sub>conv</sub> cells) and convert suppressed T<sub>conv</sub> cells into iT<sub>R</sub>35 in an IL-35-dependent manner. Mechanistically, trophoblast cell derived IL-35 mediates its function through phosphorylation of STAT1 and STAT3. In vivo studies confirm that mice with immunologically spontaneous abortion have lower levels of IL-35 and iT<sub>R</sub>35 cells at the maternal-fetal interface, and neutralizing anti-IL-35 mAb enhances abortion rates. Meanwhile, exogenous IL-35 induces iT<sub>R</sub>35 and prevents immunological abortion. Our findings thus suggest that trophoblast cells have a critical function in preserving maternal-fetal tolerance via secreting IL-35 during pregnancy.

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