PTPA and pulmonary fibrosis: In the context of COPD and allergic airway diseases triggered by allergens such as dust mites or egg proteins, TNF-related apoptosis-inducing ligand (TRAIL) can alleviate pulmonary fibrosis by up-regulating MID1 (E3 ubiquitin ligase), which inactivates protein phosphatase 2A (PP2A) (132).