The structural features responsible for the immunogenicity of certain parts of native protein molecules have been of interest to immunochemists and protein chemists for over three decades. Following the early work of Land- steiner in 1942, which showed that peptide fragments from silk fibroin exhibited an inhibitory activity toward the reaction of the protein with its antibodies, fragments from many other protein systems have been isolated and studied. However, no concerted effort was (or could be) devoted to the elucidation of the complete antigenic structure of a protein. In order for these...