The Precipitation Reaction: Optimal Proportions, Neutrality and Maximal Precipitation in Mixtures of Albumin and Antiserum

Abstract

INTRODUCTION. CULBERTSON (1932) has recently described a method for estimating the antibody content of antisera against crystalline egg-albumin. He determined by tests on supernatant fluids the point at which antigen and antibody neutralised each other. At this neutralisation point he found that antigen and antibody combined in a ratio of 1 to 13, and that the amount of precipitate nitrogen was maximal. The ratio 1 to 13, he stated, held for all the precipitates in the post-zone where antibody was in excess.The optimal proportions method of titrating either antigen or antibody in the precipitation reaction, described for horse serum and its antisera by Dean and Webb (1926), was believed to indicate the proportions of the reagents which neutralised each other. In contrast to Culbertson's finding Dean and Webb reported that maximal precipitation occurred not at their optimal or neutral point, but where excess of antigen was present.The present communication records studies made to establish the relationships of the points of neutrality, constant-antibody (Dean and Webb) optimal particulation, and maximal precipitation. The point of maximal precipitation for antisera to crystalline egg-albumin has been determined with precautions calculated to increase the accuracy of the measurements. Additional experiments have been carried out with antisera to crystalline horse-serum albumin. In the experiments of Culbertson and of Dean and Webb the amount of an antiserum was held constant and that of the antigen varied. In order to obtain a more rigorous test of Culbertson's conclusion that there is a constant ratio of antigen nitrogen to precipitate nitrogen of 1 to 13 in the zone of

A Quantitative Theory of the Precipitin Reaction

“…Taylor, Adair, and Adair (9) have doubted the validity of the assumption made in earlier papers of this series that all of the added antigen is precipitated in the presence of antibody excess. Opportunity for an experimental verification of this assumption was furnished by the use of thyroglobulin, a single antigenic substance containing iodine, an element which could be estimated quantitatively in the specific precipitates.…”

“…The reasons for this assumption were fully given in (6) but its validity was questioned by Taylor, Adair, and Adair (9). Since the iodine content of the Tg used was accurately known and anti-Tg had been found to be free from iodine, it was possible to precipitate a given amount of Tg iodine with an excess of antiserum and determine the proportion of the iodine in the washed specific precipitate.…”

The antigenic behaviour of serum proteins with special reference to crystalbumin and seroglycoid

“…Two zones of precipitation with serum proteins were ascribed by Goldsworthy & Rudd [1935] to globulin and albumin respectively. Indirect evidence of the complexity of the serum albumin fraction [Taylor et al 1934] was attributed by Goldsworthy & Rudd to the presence of globulin.…”

The Precipitation Reaction. Experiments with an Antiserum Containing Two Antibodies

“…The antigens used were egg albumin, crystallised seven times as described by Taylor, Adair and Adair (1932), and horse serum albumin four times crystallised according to the method of Adair and Robinson (1930). Both antigens contained 15-6 per cent.…”

“…Since Taylor, Adair and Adair (1934) showed that the weights of such precipitates could be accurately determined from estimations of their nitrogen content, the precipitates have been expressed in terms of their nitrogen content.…”