IFNG and hydrops fetalis: IFNγ-treated HF-MSCs exhibited significantly higher IDO expression compared with the untreated cells at both the mRNA—p < 0.001 each passage compared with its control—and protein levels—p < 0.001 passage 2 compared with its control, and p < 0.01 passage 10 compared with its control—with no statistical differences (p > 0.05) between passages (Figure 3B,C and Figure S4).