The Value of Diluted Antigen in the Wassermann Reaction.

This paper reports an attempt to assess the value of a modification of the Wassermann reaction wherein a suitable dilution of the normal antigen together with an increased amount of serum was used in an additional tube as suggested by Richardson (1940). By this method we hoped, first, to be able to differentiate specific reactions in sera giving doubtful results with the standard Wassermann technique from non-specific reactions, and, secondly, to detect weakly positive sera in cases of treated syphilis. Sordelli (1931), by using two strengths of lipoidal emulsion as antigen in combination with two strengths of serum, showed that the specificity of the Wassermann reaction could be greatly increased. Richardson -(1940) adapted the WylerHarrison technique accordingly and improved the specificity of the Wassermann reaction in doubtful cases and at the same time maintained the sensitivity as compared with the standard WylerHarrison technique. Vaughan (1947) recently published results agreeing with those of Richardson and found that both the specificity and sensitivity were increased by the new method. Both Richardson and Vaughan compared the standard Wassermann reaction with the modified technique whereas we have used this method as a verification test for doubtful sera and as a more sensitive test for weakly positive sera. The theoretical basis of the modified test as suggested by Richardson is as follows. There is abundant excess of specific hapten present in the lipoid extract; therefore with weakly reacting sera the excess of specific hapten in the usual antigen (1.: 15 dilution of the lipoid extract) might produce zonal inhibition which would be overcome by using a diluted antigen (1: 90 to 1: 150 dilution of the lipoid extract). Combining proportions of antigen and antibody would thereby be nearer the optimum. Further, at such high dilutions the strength of any contaminating non-specific hapten or haptens should be too low to fix a full dose of complement. So, by using the usual antigen in one tube and in another the antigen diluted 1: 6 to 1 :10, the specific and non-specific reactions should be more easily distinguished.A specific reaction which is partly suppressed by zone inhibition with the usual antigen should be enhanced with the diluted antigen where proportions are nearer the optimum, whereas a non-specific reaction which is partial with the usual antigen should be weakened with the diluted antigen, provided. that any contaminating hapten is not present in sufficient. strength to fix a full complement dose when the antigen is diluted.