Antigenic specificity of human alveolar macrophages and blood monocytes studied by an immunofluorescence technique

Lung alveolar macrophages (AM) and blood monocytes (BM) are part of the mononuclear phagocyte system (MPS) and have been shown to be composed of several functionally and biochemically distinct subsets. AM and BM were each fractionated into four subfractions by centrifugation over Percoll, 95 per cent of the monocytes having a higher buoyant density than the high-density AM fraction. Antigen distribution within the cell subfractions was studied by an immunofluorescence technique using a panel of ten monoclonal antibodies (MoAbs) reacting with separate antigenic determinants previously found on mononuclear phagocytes. Several antigens were present on both types of cells (Ki-M1, Ki-M6, Leu-M3, Leu-M5, 1D5, Dako-Ma, and HLA-DR), while other antigens were expressed exclusively on BM (MAS 072 and MAS 081) or on AM (Ki-M8). Ki-M1, Leu-M3, Leu-M5, and HLA-DR were expressed to a greater degree on the surface of AM (95-96 per cent of cells) than on BM (56-68 per cent), while an inverse relationship was noted for 1D5 antigen (present on 41 per cent of BM and 11 per cent of AM). Ki-M6 and Dako-Ma MoAbs recognized an intracellularly restricted antigen present in both AM and BM. Ki-M1, Ki-M8, MAS 072, MAS 081, Leu-M3, Leu-M5, 1D5, and HLA-DR were expressed both in the cytoplasm and at the cell surface. Some antigens (1D5, Leu-M3, MAS 072, MAS 081, and Dako-Ma) showed an uneven distribution among subsets of both AM and BM.(ABSTRACT TRUNCATED AT 250 WORDS)