The phagocytic response of alveolar cells is a significant factor in determining the pulmonary distribution and fate of inhaled, insoluble particles. The type I alveolar epithelium and alveolar macrophage readily phagocytized inhaled nickel monoxide and chromic oxide particles with 80% and 91%, respectively, of alveolar deposits being found in macrophages and 0.5% and 4.2%, respectively, being localized in type I alveolar epithelium. Type II alveolar epithelium did not exhibit any phagocytic activity. Fewer NiO particles were found in macrophages, and more were found free in alveolar lumens following exposure to cigarette smoke, indicating an inhibition of phagocytosis of inhaled particles by cigarette smoke.
Sanders CL, Jackson TA, Adee RR, Powers GJ, Wehner AP. Distribution of Inhaled Metal Oxide Particles in Pulmonary Alveoli. Arch Intern Med. 1971;127(6):1085-1089. doi:10.1001/archinte.1971.00310180101014