Protein antigens of mycobacteria studied by quantitative immunologic techniques.

Crossed immunoelectrophoresis has great resolving power in the demonstration of immunogenic constituents of mycobacteria. The pattern with multiple precipitate lines is highly reproducible and allows precise identification of components. After the isolation of individual proteins, immunologic specificity combined with molecular weight determination and N-terminal amino acid sequencing should be used to ensure consistent identification in different laboratories. Simultaneous quantification of individual proteins in sonicates of washed bacilli and culture fluids permits the determination of a localization index, which indicates whether the proteins are cytoplasmic constituents or actively secreted. Several "new," actively secreted proteins have recently been defined, and the role of these proteins in the interaction between the bacilli and the infected host is discussed.