Abstract
Recent work has shown that certain antitoxins can be partially digested 1 with pepsin without losing their abilities to neutralize toxin. The chemical changes 2 that accompany this alteration are apparently small; the immunological modification 3 is, however, clearly set forth in the seriously impaired antigenicity of digested antitoxins. We have made electrophoretic studies of a number of such digested antitoxic sera. In this way it has been possible to follow the course of the enzymatic digestion and to obtain an objective record of the changes that occur when sera are modified.
In these experiments diphtheria and tetanus antitoxic horse sera have been digested with pepsin at 37°C and pH 4. Electrophoretic analyses have been made of the original sera and of samples of the digest mixture taken at various intervals during the digestion process.
Previous work has shown that powerfully antitoxic horse sera contain large new T-components 4 which develop during the course of hyperimmunization. Such a T-peak appears in the electrophoretic pattern of the diphtheria and tetanus antitoxic sera shown in Figs. 1 and 4. A study of areas and mobilities in the electrophoretic diagrams demonstrates that during digestion this T-component is more or less rapidly converted into a slower component that moves at substantially the same rate as the normal γ-globulin. As can be seen from Fig. 2 no T is left in a diphtheria antitoxin after one half hour's digestion. A great advantage of digested antitoxin lies in the comparatively slight reactions that follow its injection into man; in order to modify it to this extent, however, a serum must be digested for many hours. Loss of reactivity is not therefore the immediate consequence of the transformation of the T-globulin.
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