Which of the following statements concerning alveolar macrophages is true?: (A) They secrete a1-antitrypsin., (B) They secrete elastase., (C) They originate from blood neutrophils, (D) They may play a role in causing hyaline membrane disease
Answer is B. Alveolar macrophages secrete elastase. Normally, a1-antitrypsin, a serum protein, interacts with elastase, thereby protecting the lung against damage that may lead to emphysema.