Antigenic Properties of Some Azo Compounds of Serum Albumin and Serum Globulin

Abstract

Mulinos and Schlesinger 1 have shown that when the proteins of egg white or of homologous blood serum are linked to antipyrine through an azo group,∗ the resulting compounds are antigens capable of eliciting precipitins in rabbits and shock or uterine spasm in guinea pigs. The present report relates to similar experiments with analogous antigens prepared by coupling diazo compounds with homologous serum albumin and globulin.

The results with the azo proteins from serum albumin were analogous to those obtained with whole serum, in that precipitative reactions were readily obtained and were inhibited by the preliminary addition of the original amino compounds employed for the preparation of the azo proteins. On the other hand, the azo derivatives of serum globulin failed to display antigenic character.

The serum albumin and globulins, prepared in the usual manner by precipitation from saturated and half-saturated ammonium sulfate solution respectively, were coupled in weakly alkaline solution, according to the procedure of Landsteiner and Lampl, 2 with the diazo compounds prepared from 4-amino antipyrine and anthranilic acid. After 2 hours at low temperature the mixture was acidified with acetic acid. The flocculent protein was repeatedly redissolved, then reprecipitated by acid, until the supernatant liquor remained colorless. The final azoprotein solutions were made up to contain 10 mg. of protein per cc.

The effects of precipitins from rabbits upon the 4 types of azo protein are shown in Table I; inhibition by amino antipyrine and anthranilic acid is shown in Table II. The cases in which the azo groups showed antigenic reactions may be ascribed to the presence of serum albumin as a contaminant in the original globulin. It is of interest that the azo globulins were approximately twice as intensely colored as the azo albumins.