Properties of TAS-1D3, a tuberculin-active substance from BCG, in regard to delayed hypersensitivity

The properties of TAS-1D3, a tuberculin-active substance purified from the cell extract of Mycobacterium bovis BCG, were studied in vivo and in vitro. In the delayed hypersensitivity skin reaction, TAS-1D3 showed far more potent activity than tuberculin purified protein derivative (PPD) in guinea pigs sensitized with BCG vaccine. This was consistently observed from 6 to 24 weeks after sensitization. The histological findings of the skin reaction to TAS-1D3 were similar to those of the reaction to PPD. Moreover, TAS-1D3 induced well both thymidine incorporation and the production of migration inhibitory factor (MIF) by the spleen cells from guinea pigs sensitized with BCG vaccine. In contrast, TAS-1D3 showed weaker activity than PPD in guinea pigs sensitized with either heat-killed M. tuberculosis Aoyama B or heat-killed M. tuberculosis H37Ra, and it weakly stimulated the spleen cells from animals sensitized with M. tuberculosis Aoyama B to incorporate thymidine and to produce MIF.