Results of parallel tests with the Reiter protein complement-fixation test, the treponemal immobilization test. and the treponemal Wassermann reaction on 1,046 sera.

The Treponemal Immobilization Test (TPI) is now generally accepted as a highly sensitive and specific test for treponemal infection, but its complexity and the difficulties inherent in the use of a living organism as antigen have restricted its performance to specialized laboratories. These limitations have led to the re-investigation of the cultivable strains of treponemes as antigens for the serological diagnosis of syphilis. Most workers have used the Reiter treponeme as a source of antigenic material as it is avirulent and is easily grown in artificial media. Phenolized suspensions were used by Gaehtgens (1929) and despite conflicting reports of their specificity were widely used by continental workers before the second world war. Comparisons of the results given by tests using suspensions of the intact organism as antigen with the TPI showed that such suspensions had a higher specificity and sensitivity than the classical serological tests for syphilis (STS) performed with lipoidal antigens (Benazet, Brottes, Thivolet, and Sohier, 1954; Sohier, Benazet, Brottes, and Thivolet, 1954; Hardy, Bornand, and Durel, 1955; Gastinel, Vaisman, and Hardelin, 1956; Wilkinson, 1957). Suspensions of the Reiter treponeme disintegrated by ultrasonic waves have also been found to be good antigens (Fuhner and Gaehtgens, 1954; Vaisman, Hamelin, and Prudhomme, 1958). The preparation of four chemical fractions from the Reiter treponeme was described by D'Alessandro, Oddo, Comes, and Dardanoni (1949) and D'Alessandro and Dardanoni (1953). They isolated protein and carbohydrate fractions and two lipoids, one of which reacts with the reagin antibody detected by the