Endotoxin-induced neutrophilic alveolitis and macrophage chemotaxin production in sheep.

The mechanism(s) responsible for endotoxin-induced pulmonary leukostasis has not yet been elucidated. We studied ten unanesthetized sheep by performing serial bronchoalveolar lavages (BAL) before and after infusing Escherichia coli endotoxin to determine whether or not neutrophils appeared in the airways and whether or not endotoxemia stimulated alveolar macrophages to produce neutrophil chemotactic activity. The absolute number and percentage of neutrophils recoverable by BAL increased significantly at 24 hours after infusion of endotoxin. Alveolar macrophages isolated from the BAL of sheep after endotoxemia produced a substance that is chemotactic for neutrophils, a response that is also maximal 24 hours after endotoxin infusion. We conclude that endotoxemia causes migration of neutrophils into lung air spaces and that this response may result from in vivo production of a chemotactic factor(s) by activated alveolar macrophages.