INTRODUCTION: Maternal immune system tolerance to the semi-allogeneic fetus is 
critical to a successful pregnancy. We previously reported that myeloid-derived 
suppressor cells (MDSC) was associated with maternal immune imbalance. T cell 
immunoglobulin and mucin-containing protein 3 (Tim-3)/Galectin-9 (Gal-9) pathway 
modulates function of various immune cells in maternal-fetal interface. However, 
the regulatory effects of Tim-3/Gal-9 signaling on MDSCs and its role in 
preeclampsia (PE) remain unclear.
METHODS: In the current study we investigated the expression of Tim-3 on MDSC in 
preeclampsia (PE) patients to further explore the pathogenesis of PE.
RESULTS: The proportion of Tim-3+ M-MDSC (monocytic MDSC) cells was higher in PE 
patients than in healthy control. Meanwhile, the protein expression of Gal-9, as 
the ligand of Tim-3, was increased in placenta of PE patients. M-MDSC also 
expressed a higher level of interferon-γ (IFN-γ) and a lower level of 
transforming growth factor-β (TGF-β) in PE. Furthermore, our study suggested 
that blocking Tim-3 could attenuate the inhibitory function of MDSC.
DISCUSSION: The abnormal expression of Tim-3 on MDSC might be involved in the 
pathogenesis of PE, and could be a marker to evaluate the immune function in PE.