Whereas bifidobacteria were virtually absent in WT and IFN-γR−/− (HO) mice, bifidobacterial 16S rRNA levels were significantly higher in IFN-γ+/− (HE), Rag1−/− (HO), Rag1+/− (HE), and IL-4−/− (HO) mice as compared to WT controls (mean differences up to 3.5 orders of magnitude; p<0.005–0.0005; Fig. 2B). The gene discussed is IFNG; the disease is hereditary elliptocytosis.