Immunochemical analysis of tuberculin purified protein derivative with special reference to United States-Japan antigen 7.

Immunochemical analysis of tuberculin purified protein derivative (PPD) by crossed immunoelectrophoresis and other agar gel techniques revealed substantial variation in antigen levels among PPDs and significant differences that were dependent upon the antiserum used. D-Arabino-D-mannan was identified as a major polysaccharide constituent of PPD; D-arabino-D-galactan and United States-Japan antigen 6 were also present. United States-Japan antigen 7 was found to be a major anodal constituent of all preparations of PPD. This antigen was purified and demonstrated to be a molecularly heterogenous small protein or large peptide with an average molecular weight of approximately 8,000. Antigen 7 possessed tuberculin activity with about one fourth the potency of PPD. When studied in animals sensitized with Mycobacterium tuberculosis and Mycobacterium kansasii, antigen 7 displayed no more tuberculin specificity than PPD.