Summary
The titer of treponemal immobilizing antibody in syphilis serum may be determined by measuring the serum dilution which produces immobilization of 50 per cent of the treponemes after 18 hours incubation at 35 C.
The occurrence of false positive and false negative results described in the text may be detected and avoided by careful attention to: 1) removal of rabbit testicular syphilomas in the stage of early orchitis; 2) adequate controls in each individual experiment, consisting of known negative and known positive serum controls; and 3) examination for the presence of residual C′ in all test mixtures in which immobilization fails to occur.
Modifications in the medium used for isolating and sustaining Treponema pallidum in vitro are described.
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