Option A (Alveolar macrophage) is correct. The alveolar macrophage wanders over the alveolar surface phagocytosing inhaled particles. This is the only place in the body where macrophages migrate over a surface area; elsewhere, they migrate within connective tissue. These cells are “free” and are located on the air surface of the respiratory membrane. As a result, they are easily captured by saline lavage of a pulmonary lobule or bronchopulmonary segment.
Option B (Endothelial cell) is incorrect. Endothelial cells line the walls of capillaries; they would not be exposed to the saline solution.
Option C (Goblet cell) is incorrect. Few, if any, goblet cells would appear in a lavage of a bronchopulmonary segment because these cells are attached to their basal lamina.
Option D (Pneumocyte, type I) is incorrect. Few (if any) type I and type II pneumocytes would appear in a lavage of a bronchopulmonary segment because these cells are attached to their basal lamina.
Option E (Pneumocyte, type II) is incorrect. Few (if any) type I and type II pneumocytes would appear in a lavage of a bronchopulmonary segment because these cells are attached to their basal lamina.