Acton, Jean D. (Bowman Gray School of Medicine, Winston-Salem, N.C.), and Quentin N. Myrvik. Production of interferon by alveolar macrophages. J. Bacteriol. 91:2300-2304. 1966.-Rabbit alveolar macrophages inoculated with parainfluenza-3 virus in vitro produce a viral inhibitor which possesses the properties of interferon. The interferon is nondialyzable, is stable at pH 4, is not sedimented at 100,000 x g, exhibits species specificity, and can passively protect other alveolar macrophages from infection with virulent rabbitpox virus. The possible significance of alveolar macrophage-produced interferon is discussed.