Acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) is a fatal condition with high mortality (over 80%). Its etiology and pathogenesis remain unknown. There is a lack of effective treatment for it. Based on the investigators' long-term clinical observation, most cases of AE-IPF initially got "common cold" and had coryza, more cough, nasal obstruction，rhinorrhea, sore throat, some patients had fever, headache, and etc. Some of these patients' condition developed very rapidly and then became very severe similar to the situation of acute respiratory distress syndrome (ARDS). Why these AE-IPF patients were so hypersensitive to "cold"? What were the immunologic and pathological mechanisms of their lung lesions after patients exposed to "common cold"? How to effectively offer interventional treatment for AE-IPF? All the above questions are yet to be explained clearly.