MOLECULAR WEIGHT, ELECTROCHEMICAL AND BIOLOG- ICAL PROPERTIES OF TUBERCULIN PROTEIN AND POLYSACCHARIDE MOLECULES

It is of fundamental importance to obtain as nearly complete an understanding as possible of the size and other physical properties of the molecule or molecules in tuberculin which are able to elicit the tuberculin reaction. Not only is such knowledge of great value in the preparation of a pure product and in further attempts to explain the cause of the tuberculin reaction itself and its relationship to the disease, but also it will be helpful in interpreting a whole series of similar immunological reactions of which the tuberculin reaction is a prototype. The differences observed between the tuberculin reaction (the delayed type of reaction) and typical protein sensitiza- tion reactions (the immediate type) may well depend upon some physical property of the molecule, for both are obviously elicited by constituents in the tubercle bacillus culture filtrates. Throughout this study, therefore, the relationship in various prepa- rations between tuberculin potency and antigenicity, on the one hand, and molecular weight or shape and electrochemical properties, on the other, was noted, and the aim was to prepare homogeneous frac- tions having certain of these different properties. The separations were rendered dii~cult because of the large amount of polysaccharide