Peroxidase activity in human alveolar macrophages demonstrated by 3-amino-9-ethyl-carbazol as substrate

Airdried smears of routine sputa, bronchial secretions, and bronchus lavages were incubated to demonstrate peroxidase activity in the alveolar macrophages, with 3-amino-9-ethyl-carbazol as substrate. In light microscopic examination two deposition patterns of reaction product could be found: Reaction product only to be found on, resp. in the nuclear membrane; Reaction product deposited in granules throughout the cytoplasm, some cells being totally loaded. However, most of the alveolar macrophages did not show any peroxidase activity. Thus the population of alveolar macrophages comprises resident and exudate forms.