Immunogenicity of Particles Isolated from Mycobacterium tuberculosis

Summary1. By following a carefully standardized procedure highly immunogenic particles uniformly were obtained by ultra-centrifugation from ground extracts of the H37Ra strain of Mycobacterium tuberculosis var. hominis. These particles, which ranged in size from 20-200 mμ, were just as effective as the living whole cells of this strain in protecting mice against a severe tuberculous infection. 2. The sediment comprised of the particles prepared from H37Ra cells was red in color and therefore has been 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 M sucrose buffer, autoclaved at 126°C for 15 minutes, or filtered through a Berkefeld filter. However, lyophilization in 0.25 M sucrose buffer significantly reduced their immunogenic activity while lyophilization in 0.88 M sucrose buffer did not. Sonic oscillation appeared to have no significant effect on the activity of the particles. When the cells were washed ...