IL4 and idiopathic pulmonary fibrosis: In ILD, CD8+ T cells are known to diffusely infiltrate the parenchyma of fibrotic IPF tissues and can differentiate into subtypes that either produce IFN‐γ but not IL‐4 (which may mitigate fibrosis) or IL‐4 but not IFN‐γ (which could promote fibrosis) [15].