Determinant competition during the immune response to N-acyl derivatives of ox insulin in the Hartley guinea-pig.

Subgroups of female Hartley guinea-pigs were immunized with N-carbamylated ox insulin, N-maleylated ox insulin, N-phthaloylated ox insulin, or with the crystalline ox insulin from which the N-acylated insulins had been prepared. The immunogens were administered in water-in-oil emulsions containing pertussis vaccine as adjuvant. Sera obtained 20 days after secondary immunization were assayed for their antibody titres to iodo-ox insulin and their insulin-binding capacities. The data were log transformed for statistical comparison. N-carbamylated ox insulin seemed to be as immunogenic as crystalline ox insulin and no specific carbamyl hapten antibody could be found. N-maleylated and N-phthaloylated ox insulins yelded significantly less antibody cross-reactingwith iodo-ox insulin, but produced a complementary quantity of specific maleyl and phthaloyl hapten antibody respectively. Thus it was shown that in the system used the immune response was partitioned between different determinants, ox insulin and its N-acylated derivatives being equipotent immunogens.