Cellular influx and activation increase macrophage cytotoxicity and interleukin-1 elaboration during pulmonary inflammation in rats.

This study was undertaken to investigate the effects of pulmonary inflammation induced by bacillus Calmette-Guérin (BCG) on the density distribution of lavaged alveolar macrophages. We sought to determine macrophage cytotoxicity and interleukin-1 elaboration in density-defined subpopulations of macrophages during tissue inflammation. At all time points after intravenously administered BCG, lavaged alveolar macrophages contained increased percentages of higher density cells. Alveolar macrophage cytotoxicity against the rat sarcoma cell line XC increased maximally 2 to 6 days after intravenous administration of BCG before declining on Day 13. Macrophage interleukin-1 elaboration increased maximally 14 days after administration of BCG before declining on Day 23. Additionally, macrophage cytotoxicity and interleukin-1 elaboration were increased above normal in cells from each of five density fractions. We conclude that a subpopulation of higher density macrophages, probably recently derived from blood monocytes, accumulates in inflammatory sites. Cellular activation increases the cytotoxicity and interleukin-1 elaboration by macrophages in all density-defined subpopulations and obscures the relationship between cellular density and function that is present in normal animals.