CD4 and chronic obstructive pulmonary disease: Nevertheless, interest in the role of autoimmunity in the pathophysiology of both IPF and COPD was revived by recent studies reporting highly activated and proliferative CD4+ cells [11] and global numerical and functional impairment of T regulatory cells [12], as well as presence of circulating auto-antibodies against nuclear and cytoplasmic antigens in both IPF and COPD patients [13,14].