Analysis of cells of the mononuclear phagocyte series in experimental mycobacterial granulomas by monoclonal antibodies

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Abstract
Two distinct types of granulomas were produced in the draining lymph nodes by immunizing guinea pigs with M. bovis BCG or M. leprae. In the BCG-induced granuloma, there is successful containment, killing and degradation of the organisms with the presence of epithelioid cells and fibrosis. M. leprae induces a granuloma where there is an absence of organization of the cells, failure to completely degrade the organisms, absence of epithelioid cells and minimal fibrosis. By using a macrophage-specific monoclonal antibody and an anti-Ia monoclonal antibody and applying the immunoperoxidase, immunofluorescence and fluorescence-activated cell sorter analysis techniques, the epithelioid cells of the BCG granuloma were found to have macrophage-specific antigen, but not detectable amounts of Ia antigen. Apparently, these cells have a close relationship to other cells of the mononuclear phagocyte series with which they share a common antigen. The absence of Ia antigen suggests that epithelioid cells may not be involved in antigen presentation or other accessory cell functions where the presence of Ia antigen is crucial. The macrophages in the M. leprae-induced granuloma expressed both macrophage-specific and Ia antigens.