Chemotactic and mitogenic components of the alveolar macrophage response to particles ad neutrophil chemoattractant.

The pulmonary response to instilled particulates involves initial efflux of polymorphonuclear leukocytes (PMNs) and increased production of alveolar macrophages (AMs). The relationships of the cell migration and division components of the AM production to the initial PMN response after intrapulmonary carbon or latex administration are examined. Supernatants of lung lavages taken during early PMN migration to the alveoli promote sequential migration of PMNs, migration of monocytes, and division of pulmonary interstitial cells in normal mice. Supernatants taken during the phase of increased cell division in the lung produce no such effects, implying tht factors responsible for chemotaxis and mitosis are generated rapidly and are short-lived. A possible source is the interaction of AMs with particles, since supernatants of such incubations induce an inflammatory response in vivo. Similarly, when a synthetic chemoattractant is used, efflux of PMNs is followed by macrophages arising from migration of monocytes and from division of interstitial cells. The results suggest that particulate instillation in the lung stimulates a standard inflammatory response in which rapid generation of a factor(s) chemotactic for PMNs also attracts mononuclear cells to the alveoli. The initial efflux of cells may be explained by migration from the blood, but continued demand or replacement requires mitotic activity of precursors. For the alveolar macrophages, this includes division of cells in the pulmonary interstitium.