title: Differences in epitope restriction of autoantibodies to native human insulin (IAA) and antibodies to heterologous insulin (IA).
abstract: The binding profiles of insulin autoantibodies (IAA) and insulin antibodies (IA) to highly purified species variants and fragments of insulin were studied in direct immunospecific enzyme-linked immunosorbent assay (ELISA) and indirect absorption experiments with insulins covalently coupled to Sepharose beads. Five of 10 IAA-containing sera from insulin-naive nondiabetics that bound whole human (H) insulin did not bind whole porcine (P) or whole bovine (B) insulins. These sera bound H insulin B-chain but not P B-chain or desalanated P insulin, suggesting they were dependent on the presence of threonine B30. The other 5 IAA-containing sera bound H, P, B, and desalanated porcine insulins, but only 1 bound isolated B-chains. All 10 IA-containing sera from insulin-treated diabetics bound H, P, B, and desalanated P insulins, but only 1 bound to human (and porcine) B-chain. Further binding studies with ovine, rabbit, rat, and guinea pig insulins confirmed the H (threonine B30) specificity of the 5 IAA-containing sera. B30 residues do not appear to be dominant, however, when insulin is administered exogenously. Instead, IA bind predominantly to A-chain or conformational determinants involving both chains. Scatchard analysis of a representative H insulin-specific IAA serum suggested that it contained a single binding affinity, whereas analysis of a representative IA-diabetic serum suggested it contained several different affinities.
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D001323:Autoantibodies / Q000276:immunology*; D002417:Cattle; D000939:Epitopes / Q000276:immunology*; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D007330:Insulin Antibodies / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D011817:Rabbits; D051381:Rats; D012756:Sheep; D013552:Swine
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D007330:Insulin Antibodies