Immunogenicity of Particles Isolated from Mycobacterium tuberculosis.

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Abstract
By following a carefully standardized procedure highly immunogenic particles were uniformly obtained by ultra-centrifugation from ground extracts of the H37Ra strain of M. tuberculosis var. hominis. These particles, which ranged in size from 20-200 mu, were just as effective as the living whole cells of this strain in protecting mice against severe tuberculous infection. The sediment comprised of the particles prepared from H37Ra cells was red in color and was termed the "red fraction." The immunogenic activity of this fraction was almost eliminated when the particles were diluted 5 times or more with 0.25 [image] sucrose buffer, autoclaved at 126[degree]C for 15 minutes, or filtered through a Berkefeld filter. However, lyophilization in 0.25 [image] sucrose buffer significantly reduced their immunogenic activity while lyophilization in 0.88 [image] sucrose buffer did not. Sonic oscillation appeared to have no significant effect on the activity of the particles. When the cells were washed 3 times with sucrose buffer the immunogenic activity was not affected. In contrast to these findings, even though the same preparation procedures were followed, the fraction containing the particles when prepared from BCG cells was not always immunogenically active. The sediment containing the particles appeared gray in color, and the immunogenic activity was reduced by sonic vibration and by washing with sucrose buffer. A chemical analysis of the particles from both H37Ra and BCG showed that they contain large amounts of lipid and no DNA. The significance of these findings is discussed.