To determine whether the protective effect of L. reuteri on BPD is mediated by IL-22, L. reuteri and anti-IL-22 antibodies were administered to hyperoxia-induced mice, and the results showed that the protective effect of L. reuteri on BPD could be inhibited by an anti-IL-22 antibody. The gene discussed is IL22; the disease is bronchopulmonary dysplasia.