In summary, CD46 plays a protective role against emphysema/COPD by restraining the CD8+T cells proliferation and the complement cascade through production of Tregs that regulates the ratios of CD4+/CD8+ T cells and simultaneously regulating C3b deposition favoring apoptosis over necrosis, thus, protecting this subjects from autoimmunity and chronic inflammation. Here, C3 is linked to pulmonary emphysema.