Characterization of the subsets of human NKT-like cells and the expression of Th1/Th2 cytokines in patients with unexplained recurrent spontaneous abortion

•NKT-like cells were significantly higher in the PB and decidua of the URSA group.•CD3+CD56+CD16+ NKT cells in the PB were useful for the prediction of pregnancy outcome.•The ratio of decidual Th1/Th2 cytokines was significantly increased in the URSA group.•Decidual IL-4 negatively correlated with the blood and decidual NKT-like cells.

The objective was to investigate the subsets of natural killer T (NKT)-like cells and the expression of Th1/Th2 cytokines in the peripheral blood (PB) and/or decidual tissue of patients with unexplained recurrent spontaneous abortion (URSA). The percentages of NKT-like cells in the PB and deciduas of URSA patients in early pregnancy and in the PB of nonpregnant women were analyzed by flow cytometry. The expression of interferon (IFN)-γ (Th1 cytokine) and Th2 cytokines, interleukin (IL)-4 and IL-10, in the PB and decidual tissue was measured by quantitative RT-PCR and enzyme-linked immunosorbent assay (ELISA). Most percentages of subsets of NKT-like cells (CD3+CD56+, CD3+CD56+CD16+) in the PB and deciduas were significantly greater in URSA patients than in normal pregnant and nonpregnant women. A cut-off value of 3.75% for the increased percentage of CD3+CD56+CD16+ NKT-like cells in the PB appeared to be predictive of pregnancy failure. Moreover, we found that in the decidua, IFN-γ expression was significantly higher, while IL-4 and IL-10 expression was significantly lower in URSA patients compared with those with a normal pregnancy. The ratio of decidual Th1/Th2 cytokines in URSA patients was significantly increased compared with that in normal pregnant women. Decidual IL-4 expression correlated negatively with the percentages of blood CD3+CD56+CD16+ NKT-like cells and the decidual CD3+CD56+ and CD3+CD56+CD16+ NKT-like cells. NKT-like cells may play an important role in maintaining normal pregnancy. Measurement of CD3+CD56+CD16+ NKT-like cells in the PB may provide a potential tool for assessing patients' risk of spontaneous abortion.