A study of the specificity of alveolar macrophage antigen(s).

A specific antibody has been prepared in the rabbit against purified rat alveolar macrophages. Immunofluorescent and absorption tests show that rat alveolar macrophages are carriers of specific antigen(s) that are not visible in rat monocytes and free tissue macrophages (peritoneal). On the other hand, rat fixed tissue macrophages from different organs such as liver, spleen, thymus, and lymph node show high percentages of cross-reaction with the antialveolar macrophage antibody, thus revealing the presence of very similar or the same antigen(s). A certain number (about 20 per cent) of bone marrow cells also give positive reactions but their identity as either fixed tissue macrophages or precursors has not been established. A survey of the distribution of rat alveolar macrophage antigen(s) in cells of the mononuclear phagocytic system in four other animal species revealed a high degree of species specificity.