In addition, the pathologic scores of OVA-induced asthmatic mice in group D were significantly lower than those in group A, and the levels of serum IFN-γ and the IFN-γ/IL-4 ratio in OVA-induced asthmatic mice of group D were significantly higher than those in group A, implying that early-life exposure to a diverse microbial environment may prevent asthma development via regulating IFN-γ levels or the IFN-γ/IL-4 ratio. This evidence concerns the gene IL4 and asthma.