Comparison between Purified Individual Tuberculo-Proteins and the International Standard Tuberculin

A trifold method of measuring tuberculin reactions is described. It appears to be more sensitive for quantitative assessment than other methods in use and permits a more critical and valid evaluation of comparisons. Several proteins prepared from unheated tuberculin filtrates and 1 isolated from bacillary bodies (designated as A, B, C and bacillary protein) were compared at various dose levels with comparable PPD-S as skin test antigens in known tuberculous patients and in people vaccinated with a human strain vaccine ($R_{1}R_{v}$) or a bovine strain vaccine (BCG), as well as in nontuberculous but naturally sensitized individuals. The C protein fraction proved to be considerably less sensitive and possibly, less specific than the standard PPD-S in all subjects, indicating that its presence in PPD may dilute the strength. The B protein appeared to be more sensitive and possibly more specific as a skin test antigen than PPD-S.