PDCD1 and spontaneous abortion: These results provide further evidence that maternal immune cells could be educated by embryonic trophoblasts to develop a unique phenotype and maintain fetal tolerance.17, 18, 26, 27 Importantly, the number and function of Tim-3+PD-1+CD8+ T cells in decidua were significantly impaired in miscarriage, suggesting that the expression of inhibitory molecules Tim-3 and PD-1 on CD8+ T cells during pregnancy might conduce to the maintenance of maternal–fetal immune tolerance and normal pregnancy.