Differentiation of mycobacteria by "in vivo" and "in vitro" delayed hypersensitivity reactions.

Guinea pigs were sensitized with heat killed M. tuberculosis, M. kansasii, M. scrofulaceum, and M. avium-intracellulare. Purified Protein Derivatives (PPDs) prepared from each of these organisms were tested for delayed type hypersensitivity by lymphocyte transformation, macrophage migration, and mantoux type skin sensitivity tests. The homologous reactions were consistently more intense than heterologous reactions in all three procedures. The skin test procedure was more sensitive than either in vitro method. Positive skin test reactions were elicited with 2 times and 50 times less antigen than, respectively, the lymphocyte transformation and the macrophage migration tests.