Interstitial and free lung cells in acute inflammation in the guinea-pig

Different cell types were studied in bronchoalveolar lavage fluid (BAL) and solid lung tissue of guinea-pigs. Whereas alveolar macrophages (AM) and eosinophils predominated in BAL, the proportion of AM and lymphocytes was highest in the lung tissue. After an inhalation exposure to LPS, the number of neutrophils increased rapidly in the lung tissue reaching a maximum after 4 hours, and more slowly in the airways reaching a maximum after 24 hours. This suggests that other mechanisms than secretion of chemotactic factors from AM, shown to be active up to 4 hours after exposure, are responsible for the later phase of the neutrophil invasion into the airways. Passive migration or other mediators may be involved.