Abstract
The practice of heating serum to 56°C. for 30 or more minutes unquestionably increases the precipitating ability of blood serum from syphilitics for the saline suspensions of lipoid-cholesterin antigens now used in the precipitin test for syphilis. Insistence upon the use of “inactivated” serum in such precipitin tests apparently began in 1918 by Sachs and Georgi, 1 and was followed by Meinicke in his third modification in 1919, 2 and by Dreyer and Ward 3 in 1921, and Kahn 4 in 1922.
It is rather paradoxical that heating of serum should lower the “specific” antibody titre utilized in the Wassermann reaction by 75%, as shown in the now classical researches of Noguchi, 5 and simultaneously increase the precipitin titre by 8 times (from 10 to 80 Kahn units) as was recently shown by Kurtz 6 in Kahn's laboratory. The explanation advanced by Dreyer 3 of a complex antisyphilitic antibody, composed of a thermostabile precipitin coupled to a thermolabile substance which inhibits precipitins and favors complement fixation, is rather theoretical to say the least.
Kurtz quotes an apparently unpublished opinion by Nishio, a worker in Kahn's laboratory, “that the function of heating is to reduce the protective properties of the serum albumins to precipitation.” This is a most plausible theory. By advancing another purely physical method of increasing the titre of the “specific” precipitin in serum the additional evidence may be sufficient to transfer this phenomenon to terms of a simple biochemical reaction.
Using my modification 7 of Butler's antigen 8 for the slide precipitation test for syphilis I have found that by allowing the serum to dry completely the precipitating action of syphilitic serum is increased to almost identically the same extent as when heated.
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