Complement biosynthesis by human bronchoalveolar macrophages

Complement production by bronchoalveolar macrophages recovered from 8 normal volunteers and 15 patients with a variety of lung diseases was measured functionally and immunochemically. While macrophages from all eight normals demonstrated the capacity to secrete hemolytically active C2 and factor B within 48 hr of culture at consistent rates, bronchoalveolar macrophages from patients secreted C2 and factor B in widely differing amounts, and in some cases, not at all. No functional, secreted C3 was detected from normal macrophage monolayers, although apparently native C3 protein was synthesized and secreted. In contrast, functional C3 was produced by macrophage monolayers from 3 of 15 patients. These findings suggest that complement production by the normal human bronchoalveolar macrophage differs from its progenitor cell, the blood monocyte, and that complement production by bronchoalveolar macrophages may be altered in different pulmonary diseases.