These results were further confirmed by the IHC data, showing lower expressions of YY1 and PD-L1 in the placenta from the abortion-prone CBA/J×DBA/2 mice, SNAP-treated CBA/J×BALB/c mice, and mouse M1 macrophage-treated CBA/J×BALB/c mice (Figure 4F). This evidence concerns the gene CD274 and abortion.