Antibody to purified type 1-1 human serum haptoglobin was obtained in rabbits. Using this antiserum it was demonstrated that the antigenic determinants of the haptoglobin molecule reside in both α- and ß-chains. No immunological difference between the normal α1F- and α1S-chains of haptoglobin could be detected.
A number of healthy individuals whose haptoglobin pattern appeared normal by starch gel electrophoresis were shown to possess a haptoglobin which could be distinguished immunologically from the common haptoglobin types. These immunological atypical haptoglobins have been observed in individuals of types 1-1, 2-1, and 2-2. Combined immunological and chemical studies of purified haptoglobin have enabled the construction of a tentative model for the structure of human type 1-1 haptoglobin.