[A study of phagocytic cell function in aspiration pneumonia induced by carrageenan]

To estimate the changes in phagocytic cell function associated with aspiration pneumonia, induced in mice by intra-tracheal injection of carrageenan. In inflammatory sites, the dominant increased cell component was polymorphonuclear leukocytes (PMNs). Intracellular 2'-7'-dichlorofluorescein (DCFH) oxidation of PMNs infiltrated into the lung tissue of the carrageenan-treated mice revealed a lower level of activity than that of a control group throughout a 120-hour period. The DCFH oxidative activity of alveolar macrophages (AMs) was lower in the broncho-alveolar lavage fluid and lung tissue of the carrageenan-treated mice than the control group. A decrease in the DCFH oxidative activity of AMs was observed after treatment with KCN or deferoxamine in the control group. In contrast, activity in the carrageenan-treated group was not decreased by KCN. Moreover, increased expression of Ia and F4/80 antigens was detected in the AMs of the carrageenan-treated group. These results show that increasing numbers of PMNs have a major role as phagocytic cells in inflammatory lung tissue, whereas AMs are reduced to their oxidative product and change into antigen-presenting cells, revealing a high ratio of Ia expression. The decrease in DCFH oxidation in the AMs of the carrageenan-treated mice may have been due to decreased mitochondrial oxidative metabolism.