Phagolysosomal pH in alveolar macrophages from smokers and non-smokers.

1. Alveolar macrophages efficiently phagocytize particles deposited in the alveolar part of the lung. Phagolysosomal pH in alveolar macrophages from rabbits, dogs, baboons and guinea pigs is around 5 pH units. A low pH is of importance for clearance of inorganic particles and probably also for defence against bacteria and fungi. 2. Phagolysosomal pH in alveolar macrophages from smokers and non-smokers was measured using fluorescein-conjugated amorphous silica particles as a probe. pH was the same in both groups and similar to earlier studies on alveolar macrophages from animals. 3. The morphological picture between alveolar macrophages from smokers and non-smokers differed clearly with a high number of dense inclusions of great variation in size and shape in macrophages from smokers. Ingested test particles were located in all types of inclusions. 4. We conclude that phagolysosomal pH in human alveolar macrophages is similar to that in several animal species and that it is rather insensitive to influence from the environment.