Fecal samples were derived from 12-weeks-old wildtype (WT) mice, IFN-γR+/− (HE) and IFN-γR−/− (HO) mice, IFN-γ+/− (HE) and IFN-γ−/− (HO) mice, Rag1+/− (HE) and Rag1−/− (HO) mice, as well as IL-4+/− (HE) and IL-4−/− (HO) mice and subjected to 16S rRNA analysis of the most prevalent commensal intestinal bacterial groups by quantitative RT-PCR. The gene discussed is IL4; the disease is hereditary elliptocytosis.