Abstract
It has been shown 1 that specific serological reactions can be obtained with simple chemical substances, consisting of an inhibitory effect upon the precipitation of azoproteins containing corresponding chemical groups. The explanation of these inhibition reactions was obviously that the simple substances combine with the antibodies, thereby preventing the formation of a precipitate with the antigen. Direct evidence of such a combination has been claimed by Klop-stock and Selter. 2 Recently, Marrack and Smith 3 have shown that on addition of the corresponding immune serum, less of an azodye made from p-aminobenzene arsinic acid passed through a collodion membrane than when a normal serum was added. The specificity of the phenomenon was checked with another azodye (methyl red).
We have found that it is possible to obtain direct precipitation reactions with substances of simple chemical constitution. 20 The immune sera used were prepared by injecting azoproteins made from the para-amino derivatives of succinanilic, adipanilic, and suber-anilic acids. For the reactions, azodyes were used made by diazotizing the compounds mentioned above, and coupling with resorcinol or tyrosine. The concentration of the test solutions was 1:10,000 and 1:50,000.
In their specificity the reactions, particularly the group reactions of the dyes made from p-amino-adipanilic and p-amino-suberanilic acid, correspond fully to the reactions observed with azoproteins, which will be described in a later communication. There was a further correspondence in that in both cases the reactions could be inhibited specifically by the addition of the nitroanilic acids. Weak but definite precipitin reactions were also obtained with azodyes prepared from aminotartranilic acid and p-arsanilic acid, and the homologous immune sera.
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