Objective::To investigate the frequency and function of Tim-3n +CD8n +T cells in the third trimester of normal pregnancies (NPs) and preeclamptic (PE) pregnancies.n Methods::T-cell immunoglobulin mucin-3 (Tim-3) expression levels of CD8n +T cells in the decidua, peripheral blood, and umbilical cord blood obtained from women showing NPs and PE pregnancies were analyzed using flow cytometry. Decidual CD8n +T cells were cultured in the presence of recombinant human carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) protein and/or Tim-3-specific neutralizing antibodies for analyzing CD107a and intracellular cytokine expression. The placental CEACAM1 protein expression was analyzed using immunohistochemistry.n Results::Tim-3n +CD8n +T cells were more abundant in the decidua than in the peripheral blood. Tim-3 expression in the decidual CD8n +T cells was significantly lower in PE patients. Decidual Tim-3n +CD8n +T cells from PE patients expressed higher levels of CD107a and the Th1-type cytokine IFN-γ, but lower levels of the Th2-type cytokine IL-4. CEACAM1 altered the CD107a, IFN-γ, and IL-4 levels; this was reversed by anti-Tim-3 antibodies. The CEACAM1 protein levels were lower in the placental tissues of women with PE pregnancies than in those of women with NPs.n Conclusions::Abnormal CEACAM1/Tim-3 regulation may participate in the development of PE, accompanied by disturbed Th2 cell predominance and higher cytotoxicity of decidual CD8n +T cells.n “,”Objective::To investigate the frequency and function of Tim-3n +CD8n +T cells in the third trimester of normal pregnancies (NPs) and preeclamptic (PE) pregnancies.n Methods::T-cell immunoglobulin mucin-3 (Tim-3) expression levels of CD8n +T cells in the decidua, peripheral blood, and umbilical cord blood obtained from women showing NPs and PE pregnancies were analyzed using flow cytometry. Decidual CD8n +T cells were cultured in the presence of recombinant human carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) protein and/or Tim-3-specific neutralizing antibodies for analyzing CD107a and intracellular cytokine expression. The placental CEACAM1 protein expression was analyzed using immunohistochemistry.n Results::Tim-3n +CD8n +T cells were more abundant in the decidua than in the peripheral blood. Tim-3 expression in the decidual CD8n +T cells was significantly lower in PE patients. Decidual Tim-3n +CD8n +T cells from PE patients expressed higher levels of CD107a and the Th1-type cytokine IFN-γ, but lower levels of the Th2-type cytokine IL-4. CEACAM1 altered the CD107a, IFN-γ, and IL-4 levels; this was reversed by anti-Tim-3 antibodies. The CEACAM1 protein levels were lower in the placental tissues of women with PE pregnancies than in those of women with NPs.n Conclusions::Abnormal CEACAM1/Tim-3 regulation may participate in the development of PE, accompanied by disturbed Th2 cell predominance and higher cytotoxicity of decidual CD8n +T cells.n