Mycobacterial antigens relating to experimental pulmonary cavity formation

Lipid-protein mixtures were obtained from 2 strains of mycobacteria, and their cavity-forming activities were examined in rabbit lungs. The mixtures were separated into lipid and protein fractions by gel filtration on Sephadex LH-20 column. Neither lipid nor protein fraction alone had cavity-forming activity; however, restoration of the cavity-forming activity was observed by recombining the fractions. The activity was also reconstructed by combining the protein fraction with cell walls of bacille Calmette-Guérin. The protein fraction from Mycobacterium phlei was further separated into 2 fragments. The larger molecular fragment with a molecular weight of 10,000 daltons consisted of 60% protein and 40% carbohydrate and had cavity-forming activity in combination with the cell walls. The roles of lipid and protein of mycobacteria in cavity formation are discussed.