Biologically active (14)C-labeled purified protein derivative ((14)C-PPD) has been prepared from the culture filtrates of seven species of mycobacteria, namely Mycobacterium tuberculosis Johnston strain (PPD), M. bovis BCG (PPD-BCG), M. avium (PPD-A), M. kansasii (PPD-Y), M. intracellulare (PPD-B), M. scrofulaceum (PPD-G), and M. fortuitum (PPD-F). These mycobacteria were grown in a culture med...