Immunobiology and species distribution of Mycobacterium tuberculosis antigen 5.

The immunobiology and mycobacterial species distribution of immunoabsorbent affinity chromatography-purified Mycobacterium tuberculosis antigen 5 have been studied. In delayed hypersensitivity skin tests, antigen 5 was nearly equipotent with tuberculin-purified protein derivative in sensitized guinea pigs. In vitro, antigen 5 was capable of stimulating the production of migration inhibitory factor by cultured lymphocytes from sensitized guinea pigs and humans. Antigen 5 stimulated thymidine incorporation by cultured guinea pig lymphocytes but did not stimulate thymidine incorporation by cultured human lymphocytes. Although erythrocytes were readily sensitized with antigen 5 for passive hemagglutination, their use did not offer any advantage over previous hemagglutination techniques for the serodiagnosis or evaluation of patients with tuberculosis. By immunoelectrophoresis and immunodiffusion, antigen 5 was readily identified in culture filtrates of 10 strains of M. tuberculosis and M. bovis but not in those of 30 strains of 12 other myobacterial species.