Antigens of PPD, old tuberculin, and autoclaved Mycobacterium bovis BCG studied by crossed immunoelectrophoresis.

The effect of heat on mycobacterial antigens was studied by crossed immunoelectrophoresis in a system permitting identification and analysis of about 30 distinct components in Mycobacterium bovis BCG. By heating BCG concentrated culture fluid and BCG sonicates to 120 degrees C for 15 min, most antigens detectable by reaction with rabbit anti-BCG antibodies were destroyed. The BCG antigens 60, 63, 82, and 89 still gave strong precipitate lines, antigens 1B and 23 gave weak but distinct precipitate lines, whereas BCG antigens 27, 71, and 84 did not precipitate but retained some of their ability to combine with anti-BCG antibodies. Tuberculin PPD preparations showed a varying antigen content, the most prominent component corresponding to BCG antigen 60, and 6 additional components being detected in PPD RT33. The polysaccharide antigen responsible for the prominent peak of BCG antigen 89 was not detected in PPD RT 23 or PPD RT33. Only 5 distinct antigenic components were detected in Old tuberculin. They corresponded to the components remaining in autoclaved BCG, with 60 and 89 being the only prominent peaks in direct precipitation tests. The relevance of these findings concerning purification of mycobacterial antigens and the importance of individual antigenic components for induction of delayed hypersensitivity is discussed.