The effects of a bacterial endotoxin on the functional status of alveolar macrophages were studied in-vitro. Alveolar macrophages harvested by bronchoalveolar lavage from English-short-hair-guinea- pigs were incubated with 0 to 1,000 micrograms per milliliter (microg/ml) endotoxin isolated from the Pantoea-agglomerans or a saline extract of the bacteria. Cytotoxicity was assessed by the chromium-51 release assay. The effects on bactericidal activity were evaluated by determining the ability of the macrophages to phagocytize or kill Staphylococcus-aureus bacteria. The ability of the macrophages to generate superoxide anion (O2-) was assessed using the superoxide-dismutase inhibitable reduction of ferricytochrome assay. Release of interleukin-1 (IL1) was evaluated using the standard murine thymocyte proliferation assay. The effects on chemotaxis was evaluated by measuring the ability of the macrophages to recruit human neutrophils using a blind well chemotaxis chamber technique. P-agglomerans at concentrations above 100microg/ml induced significant cytotoxicity. Endotoxin concentrations of 1 to 10microg/ml enhanced macrophage bactericidal activity by 33 to 55%, while concentrations of endotoxin at 100microg/ml inhibited bactericidal activity. Production of O2- was significantly increased by the endotoxin or bacterial extract in a dose dependent manner. Both the endotoxin and extract increased macrophage chemotactic activity. Production of IL1 was increased by endotoxin or extract concentrations of 10microg/ml or higher in a dose dependent manner. The author concludes that these data should be useful for elucidating the mechanisms by which inhalation of organic dusts induces inflammatory reactions in the lung.
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