Immunohistologic analysis of mycobacterial antigens by monoclonal antibodies in tuberculosis and mycobacteriosis.

Four monoclonal antibodies (MoAbs), 60.15, 61.3, 105.10, and 2.16, directed to different proteins of Mycobacterium tuberculosis were used by an indirect avidin-biotin complex peroxidase-antiperoxidase method to detect mycobacterial antigens in lung, lymph node, and joint tissue specimens of tuberculous patients. Using MoAb 60.15, which recognizes a broad range of cross-reactive mycobacterial proteins with a molecular mass of 28 kilodaltons (kD), scattered materials (mycobacterial in origin) were observed, many of which were located within phagocyte cytoplasm. With MoAb 61.3, which reacts with a 35 kD protein present in M tuberculosis, Mycobacterium africanum, and Mycobacterium bovis, many clumped particles similar in size and shape to acid-fast bacilli were observed within the phagocyte cytoplasm (lung tissue) and positive macrophages with lysosomes were distributed throughout the cytoplasm (bronchoalveolar lavage). The specificity of this MoAb (61.3) was confirmed by the negative staining of positive lymph node specimens obtained from a patient infected with Mycobacterium kansasii. MoAbs 105.10 and 2.16 bind to the cross-reactive 65 kD heat shock protein that is present in mycobacteria and stain scattered particles and dark clumps of bacilli within the phagocyte cytoplasm. On the basis of this study, immunohistochemical detection of mycobacterial antigens appears to be useful in establishing the mycobacterial etiology of caseating granulomas and in avoiding the false-negative results obtained by traditional staining methods.