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 medium containing a mixture of
14
C-labeled amino acids. The yield and specific radioactivity of the PPD, of the nucleic acid, of the bacterial cells, and of the CO
2
developed during growth have been determined for each of the seven species of mycobacteria. Although the yields of
14
C-PPD antigens differed greatly for the different species of mycobacteria tested, their specific radioactivities were similar. The
14
C-PPD antigens have been used as a means to measure their adsorption to glass. When glass ampoules containing dilute solutions (0.001 mg of PPD per ml) of these PPD antigens (PPD, PPD-BCG, PPD-A, PPD-Y, PPD-G, PPD-B, and PPD-F) were stored for 12 months at 5 C, it was found that they all adsorbed equally well to glass surfaces. In fact, regardless of the origin of the PPD, a loss due to adsorption of about 90% occurred during the first month of storage, and thereafter the PPD content remained practically constant for the rest of the duration of the storage period. The addition of 0.0005% Tween 80 to the PPD solutions effectively reduced the adsorption to glass of most PPD antigens. However, adsorption of PPD-BCG was not quite so effectively prevented, even when the Tween 80 concentration was increased from 0.0005 to 0.0005%.