Ans. is 'a' i.e., Panacinar-emphysema Pathogenesis of Emphysemao The most accepted theory in the pathogenesis of emphysema is protease - antiprotease mechanism which is responsible in the pathogenesis of two common forms of emphysema, i.e. centriacinar and panacinar.o The alveolar wall destruction results from an imbalance between proteases (mainly elastase) and antiproteases in the lung.o Proteases (elastase) cause destruction of alveolar wall, while antiproteases prevent this damage,o a1 antitrypsin is the major antiprotease (antieiastase) secreted by neutrophils during inflammation.A. Pathogenesis of panacinar emphysemao Panacinar emphysema is associated with congenital deficiency of a1.-antitrypsin.o This results in unchecked overactivity of neutrophil elastase that causes destruction of alveolar wall,o As a,-antitrypsin is deficient throughout the acinus, the acini are uniformly involved from the respiratoiy bronchiole to the terminal blind alveoli.o Neutrophils are the major cells in the pathogenesis of panacinar emphysemaB. Pathogenesis of centriacinar emphysemao Centriacinar emphysema is associated with smoking.o Nicotine acts as a direct chemoattractant for neutrophils and macrophages,o So, in centriacinar emphysema, both neutrophils and macrophages play central role,o Smoking enhances activity of neutrophil and macrophage elastase.o Macrophage elastase is not inhibited by a1-antitrypsin and indeed can proteolvticallv digest this antiprotease,o Beside protease - antiprotease mechanism, oxidant - antioxidant imbalance also plays an important role in the pathogenesis of smoking related emphysema.o Normally, the lung contains a healthy complement of antioxidants (superoxide dismutase, glutathione),o Tobacco smoke contains abundant reactive oxygen species (free radicals) which deplete these antioxidant mechanisms.o Free radicals cause tissue damage as well as they inactivate a(-antitrypsin, resulting in functional a,- antitrypsin deficiency even in patients without enzyme deficiency.