Effect of Electrolytes upon Kahn Precipitates from Human and Animal Sera

Abstract

The problems created by the existence of falsely positive serologic reactions have been a source of difficulty since the advent of the Wassermann test. Kahn reported the first satisfactory differential test; this was based upon specific temperature differences. We became interested in determining whether or not reactions in human and animal sera could be distinguished by the effect of electrolytes. Animal sera were used in these studies because they give general biologic reactions which are apparently of the same type as those found in human falsely positive serologic reactions., while studying the effect of Nacl solutions upon the Kahn Precipitates from animal sera, it was observed that the precipitate resulting from the reaction of Kahn antigen and horse serum was soluble in 4% NaCl solution. At the same salt concentration, precipitates from syphilitic human sera remain insoluble. The effect of other concentrations of NaCl (ranging from 0% to 30%) upon horse, human, guinea pig, hog, cow, sheep, and chicken sera were investigated. All sera were diluted to give approximately two plus reactions in the standard Kahn test by a method previously described. Verification tests were made upon each serum to check the specificity of the reaction. All sera gave the expected reactions (i.e., either syphilitic, general biologic, or negative type) with this test. Controls were also made using the same quantities of serum and salt solution. However, an artificial antigen containing the same quantities of alcohol and saline as in the original antigen was used. Control reactions were completely negative except in the chicken sera. It was found that each species of animal serum investigated gave characteristic aggregation and dispersion patterns of the Kahn precipitate.