Histochemical demonstration of mycobacterial antigen, specific antibody and complement in the lesions of tuberculosis.

Lesions were studied histochemically for mycobacterial antigen, its specific antibody and complement in 31 patients with recently-diagnosed tuberculosis. The results were related to a histological spectrum that correlated with bacterial load. The form, localization and persistence of antigen were found to be as significant as the amount. In high-resistant cases, the antigen was mainly soluble, a form which was non-toxic when ingested by macrophages but associated with tissue damage when bound to connective tissue. There was no close contact between plasma cells and antigen. However, in cases with moderate resistance, where plasma cells and antigen intermingled freely, necrosis with karyorrhexis and polymorph infiltration was associated with deposition of antigen, antibody and complement at the same sites, indicating the probability of immune complex formation in these lesions. In low-resistant cases, extensive necrosis was attributed partly to high levels of extracellular antigen. The correlation between immunological circumstances and the manifold forms of necrosis validated these forms as the basis for a histological spectrum in tuberculosis.