Our study showed that the mRNA level of IL-22 was decreased in bleomycin-induced pulmonary fibrosis mice, and pulmonary fibrosis was aggravated in IL-22KO mice, whereas the addition of exogenous recombinant IL-22 reduced pulmonary fibrosis-related genes, especially Collagen I, suggesting the potential protective effect of IL-22 in bleomycin-induced pulmonary fibrosis mice. The gene discussed is IL22; the disease is pulmonary fibrosis.