The Existence of Antigenic Determinants of Diverse Specificity in a Single Protein

Summary Cross-reactions between crystalline hen- and duck-ovalbumin antigen-antibody systems are adjudged, on the available evidence, to be due to the interaction of qualitatively different antigenic determinants on single molecules and the separate antibodies engendered by them. The evidence excluding the presence of an impurity common to both ovalbumins, with its counterpart in their antisera, is presented. Other considerations are offered in support of the conception that molecularly different antibodies may be produced by immunization with molecularly homogeneous antigen.