Multiplicity of Antibody Proteins in Rabbit Anti-p-Azobenzenearsonate Sera

Rabbit antibodies against the p-azobenzenearsonate (Rp) group were studied with respect to their immunoelectrophoretic and chromatographic properties as well as their molecular size. Anti-Rp antibody activity was found in three different protein components of the antisera by the use of radioimmunoelectrophoresis with I131-Rp-insulin as a test antigen. The three antibody components, although all were directed against the same determinant group, differed in their reaction with horse antiserum against rabbit globulin. They were partially separated by gel filtration with Sephadex G-200 according to their molecular size and by chromatography on diethylaminoethyl cellulose. The antibodies of three different protein types were identified as the γ-type (6 S), the β2-type (16 S) and the β1-type (probably 9 S and 6 S). The γ-type contains γ-globulins of a wide range of electrophoretic mobility, but can be fractionated by chromatography into two distinct fractions which differ in their mobility, γ2 and γ1. It was present in all the antisera tested and carried a major part of the antibody activity. The β2-type appears to be the same as the β2 or γ1maeroglobulin previously found in rabbit serum. It was detected in most of the antisera tested. The β1-type is probably associated with the 9 S component and possibly also with the 6 S component. It seems to be the counterpart of β2A-globulin in the human. It was detected in only two of the six individual antisera tested.