Relative immunogenicity in mice of different regions of the human IgG.

Monoclonal mouse antibodies to human IgG myeloma proteins were produced and characterized by determining their binding to a series of different purified myeloma proteins. Two types of immunization schedules were used. When the same myeloma protein was used for priming and boosting the mouse, all determinants of the molecule were effectively immunogenic. Of the 353 clones originating from these experiments 42% secreted anti-Fv antibodies, 57% anti-CH antibodies, and 0.85% anti-CL antibodies. In another schedule only the CL and CH regions were the same in priming and boosting; 270 anti-CH (94%), 18 anti-CL (16%), and no anti-FV hybridomas were found. Our results indicate that a unit mass of the FV region was 1.3 times more antigenic than a unit mass of the CH region. A unit mass of the CH region was nearly five times more antigenic than a unit mass of the CL domain when the antigenicity of the FV region had been excluded. When the antigenicity of the FV region had not been excluded, a unit mass of the CH region was about twenty times more antigenic than a unit mass of the CL domain. The data suggest that an antigenic competition was taking place between different parts of the molecule and that the strongly antigenic region (FV) was more efficient in competing out the nearest neighbour (CL) than in competing out other parts of the molecule.