Strong T cell activation promotes the progression of both diseases (PCLF and IPF), with the unbalanced secretion of cytokines and chemokines being associated with the development and progression of fibrosis (IL‐4, TNF‐α, IL‐32, etc.)through the secretion of profibrotic cytokines and growth factors, facilitating collagen deposition and tissue remodeling. The gene discussed is IL4; the disease is idiopathic pulmonary fibrosis.