Hypersensitivity reactions to some synthetic dextran polypeptides in guinea-pigs.

The hypersensitivity reactions of several synthetic dextran-polypeptides have been studied in guinea-pigs. Insulin, oxidized insulin peptide B and their dextran derivatives were found to cross-react. Oxidized insulin peptide A did not cross-react with insulin or dextran-insulin peptide A. Similarly poly-L-tyrosine did not cross-react with dextran-poly-L-tyrosine. The determinants involved are discussed. An immunogenic response could not be promoted towards the carbohydrate by coupling it to polypeptides; the response was always directed towards the polypeptide. However, the immunogenicity of the polypeptide was increased by coupling it to the dextran; the effect being more pronounced for the `immediate' than for the `delayed' reaction. Sensitization with a mixture of dextran and insulin peptide B showed no enhanced `delayed' reaction but a larger `immediate' reaction than in dextran-insulin peptide B sensitive animals. It is suggested that dextran plays some part in promoting the immunogenic response, and that its effect varies according to whether or not the dextran is coupled to the polypeptide.