Spectrotypic analysis of antibodies to insulin A and B chains.

Antibodies produced by immunization with native insulin were analyzed by isoelectric focusing for binding to isolated A and B chains. Antibodies to isolated A chain of beef insulin were found to have restricted spectrotypes and were seen after immunization with either beef or human insulin. Hyperimmunization with beef insulin, but not human, increased the heterogeneity of anti-A chain antibodies. Antibodies to isolated B chains were also electrophoretically restricted but showed less heterogeneity after hyperimmunization than anti-A chain responses. When binding to chains was carried out in the presence of excess cold insulin, anti-B chain spectrotypes were inhibited by the native molecule. In contrast, only a portion of anti-A chain spectrotypes were inhibited by native insulin, suggesting that these clonotypes are directed at epitopes not present on the surface of the molecule. These data indicate that the anti-insulin repertoire includes antibodies that can bind isolated chains as well as the native molecule. Some of the determinants on isolated A chain are not available on intact insulin and may arise from antigen catabolism.