Administration of exogenous CO to pregnant HO-1-deficient mice has been shown to directly induce uNK cell proliferation possibly through the modulation of interferon-gamma (IFN-γ) and prevent the development of a pre-eclampsia-like syndrome and IUGR, independent of sFlt-1 and sEng (Linzke et al., 2014). The gene discussed is IFNG; the disease is fetal growth restriction.