Studies in tuberculosis. V. Phosphatids of tuberculin with diagnostic and sensitizing properties.

In a series of earlier publications 1 an alcohol-soluble and ether-precipitable substance, “Ether-insoluble X,” was described in connection with experiments on sensitization and diagnosis in animals and in tuberculous patients. Preliminary qualitative procedures pointed toward identifying this derivative with a phosphatid, probably lecithin, which represented a small fraction of the original old tuberculin. Typical tuberculin reactions were elicited, notwithstanding the exceedingly high dilutions that were used in the tests. It was suggested that the antigenic radical of B. tuberculosis might reside in such a fraction, and that the isolation of this derivative from tuberculin might offer a lead in the direction of explaining the mechanism of tuberculin reactions and the phenomena of sensitization which I have reported previously.

The present report is a chemical study of some lecithin-like fractions which have been obtained from old tuberculin (human) prepared from beef-extract media,∗ and from two different synthetic substrates which were described by Löwenstein and Pick, 2 and by Gessard and Vaudremer. 3 Quantitative analyses of the derivatives from these protein-free media will be published shortly. Qualitative studies have indicated that all of these derivatives are identical, and give typical skin tests regardless of the kind of media used in the preparation of tuberculin.

Tuberculin, in weighed 50 gram portions (49 cubic centimeters), was added drop by drop from a burette to pure methyl alcohol until complete precipitation was effected. Nineteen volumes of alcohol were required for each volume of tuberculin. To the clear filtrate which yielded no further precipitate, was added pure ethyl ether until complete precipitation occurred. This procedure required 3.4 volumes of ether for each volume of alcohol filtrate. The yield by alcohol precipitation from 50 grams of tuberculin was 7.45 grams dry weight, representing 14.9 per cent of the original tuberculin.