IMMUNOLOGICAL REACTIVITY OF LUNG - INVIVO AND INVITRO GENERATION OF A NEUTROPHIL CHEMOTACTIC FACTOR BY ALVEOLAR MACROPHAGES

Abstract

The generation of a chemotactic factor by guinea pig alveolar macrophages after phagocytosis of heat-killed Staphylococcus aureus was studied. After phagocytosis, alveolar macrophages secrete a small molecular weight (< 5000 daltons) chemotactic factor that preferentially attracts neutrophils. The chemotactic factor can be generated in vivo and in vitro, and its chemotactic activity can be detected in vitro by a chemotactic assay and in vivo by an increase in the absolute number of neutrophils in bronchoalveolar lavage fluid and in lung tissue histologic specimens. Generation of the chemotactic factor was inhibited by 20 .mu.g of actinomycin D/ml and by 10 .mu.g of cycloheximide/ml. The factors were stable after incubation at 56.degree. C for 45 min, but not after incubation at 100.degree. C for 10 min. Alveolar macrophages can serve as an inhibitor of pulmonary inflammatory responses by secreting a potent mediator of neutrophil locomotion.