A method has been described for the preparation of Treponema pallidum suspensions that are suitable for specific agglutination studies and can be stored at 4°C. for months without loss of agglutinability. Such suspensions have been shown to react with two distinct antibodies in the serum of syphilitic animals and man: Wassermann antibody and a specific treponeme agglutinin.

It has been demonstrated that the agglutination of treponemes by specific treponeme agglutinin is enhanced by heat treatment or aging of the suspension, and inhibited by a divalent cation, probably Ca++, normally present in serum. This inhibition has been overcome by the use of a chelating agent, ethylene-diamine tetracetate.

These findings have been utilized to devise a simple agglutination test for the diagnosis of treponeme infections that is very sensitive and highly specific. This test has been carried out with 430 human sera, and a comparison has been made of the results of the agglutination, treponemal immobilization, and standard serological tests on these sera. The agglutination test appears to have a specificity comparable to the treponemal immobilization test and considerably greater than the standard serological tests.

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