Pleural tuberculosis is often difficult to diagnose because it is a paucibacillar disease. Mycobacteria are rarely seen on direct examination of pleural fluid and pleural biopsy specimens and cultures are positive in less than 50 percent. The diagnosis is assessed by histologic examination of pleural biopsy samples which reveals granulomas. As in other limited tuberculous involvements, serum antimycobacterial antibody levels are frequently low.
Recent reports demonstrated the accumulation of T-lymphocytes reacting to mycobacterial components in pleural fluids. We tested the reactivity of the IgA and the IgG antibodies present in both pleural effusion and the corresponding serum of tuberculous and nontuberculous patients. We used a dot blot assay and the recently purified mycobacterial specific P32 antigen, identified as the 85A component of the heterogenous 85 complex in the BCG reference system.
Pleural and serum total IgG and IgA concentrations were adjusted to the same concentrations as we previously adjusted them for the study of antimycobacterial antibodies levels in cerebrospinal fluids.