PRF1 and systemic lupus erythematosus: Studies have shown that the AECA-mediated autoimmune response contributes to the development of alveolar septal cell apoptosis and COPD-associated emphysema [3–5] and that hypomethylation in the perforin gene promoter region is involved in some autoimmune diseases, such as systemic lupus erythematosus (SLE) [6] which was proven to be an important cause of COPD [7].