IL9 and idiopathic pulmonary fibrosis: More recently, a study from Li HP et al. also demonstrated that inflammatory cytokines, such as IL-6, IFN-γ, MIG, IL-17 and IL-9, were increased in the serum of AE-IPF compared with stable cases22, indicating inflammation rather than an accelerated intrinsic fibrotic process played a role in pathogenesis of AEIPF.