Inhibiting IL-22 during bleomycin injection can improve airway inflammation, indicating IL-22 has a proinflammatory effect; nevertheless, airway inflammation is also significantly reduced in IL-17-/- mice with still high levels of IL-22 produced by T cells, suggesting IL-22 has a protective function for pulmonary fibrosis in deficiency of IL-17 (79, 80). Here, IL17A is linked to pulmonary fibrosis.