Chemical and Immunological Properties of Diphtheria Toxoid Purified by Ammonium Sulfate Fractionation

A simple method for the purification of diphtheria toxoid has been presented. The products have been evaluated with respect to purity, antigenicity, and stability. Preparations having a purity in excess of 2000 Lf per mg N have been obtained. Evidence has been presented which indicates that the antigenicity per Lf increases with the purity of the toxoids studied. A linear logarithmic relationship between the flocculation time and titer at the toxoid-antitoxin equivalence point has been shown. Various relations between Lf, Kf, purity, and antigenicity have been studied.