A morphological study of the role of phagocytes in the clearance of Staphylococcus aureus from the lung.

A nonlethal dose of Staphylococcus aureus was inoculated into the mainstem bronchus of mice in order to study the influx of polymorphonuclear leukocytes (PMN). The goal was to determine the routes of entry of PMN into the lung following bacterial challenge, the relative importance of PMN as compared to alveolar macrophages (AM) in the uptake of S aureus, and the role of lymphatics in clearance of intact microorganisms. Resident AM took up S aureus within minutes of inoculation, but PMN were subsequently recruited to the lung and were the predominant cell containing S aureus by 4 hours following inoculation. PMN were recruited from arteries, capillaries, and venules. Emigration of PMN into alveolar spaces occurred between type I epithelial cells as well as between type I and type II epithelial cells. Lymphatics played only a minor role in the clearance of S aureus.