IFNAR1 and hydrops fetalis: To investigate whether the effect of PML on the expression of STAT1 and STAT2 shown in Fig. 2B involves an indirect consequence of type I IFNs, we compared the effects of PML knockdown on STAT1 and STAT2 activation after treatment of HF cells with control IgG or anti-IFNα/β receptor (IFNAR) antibody.