The relation of the fixation reaction to specific precipitation

Abstract

This work represents a continuation of studies on the mechanism of the fixation reaction between a serum and its antiserum begun by the author in 1905. It was shown that this fixation which had been attributed by Gengou to the presence of anti-albuminous sensitizers was apparently produced by the precipitate formed in the serum-anti-serum mixture. A prolific literature has since sprung up engaged principally in establishing the presence or absence of parallelism between fixation and precipitation. The results in either direction are far from conclusive.

In the present work an attempt has been made to settle the question by studying more attentively an instance in which both precipitation and fixation are known to occur, and where one may reasonably be associated with the other. It is found that in addition to the voluminous precipitate which is known to be formed by mixture of an excess of the antiserum with the antigenic serum, there is another precipitate produced with certain individual antisera in the presence of a large excess of antigen. This latter, and we believe newly recognized, zone of precipitation lies above the zone of inhibition produced, as is well known, by the ordinary excess of antigen. The upper zone precipitate differs in its granular appearance and slowness of formation from the lower zone precipitate.

No fixation of alexin occurs as a rule in mixtures representing the inhibition zone and never in presence of the upper-zone precipitate which may, however, equal or exceed in volume a precipitate of the lower zone which produces complete fixation. This fixation in the lower zone precipitate mixture is produced almost invariably by the washed precipitate and not by the supernatant fluid. The latter fluid may, however, in some cases give partial fixation.