ANTIGENIC LOCI OF INSULIN

Insulin exhibited some cross-reactivity with the isolated S-sulfo A- and B-chains in the passive cutaneous anaphylaxis test. The synthetic peptides A1-9, A10-21, and A1-21 gave a passive cutaneous anaphylactic reaction with guinea pig anti serum to natural A-chain, whereas high levels of A10-21 and A1-21 could also inhibit a subsequent insulin challenge from reacting with anti serum to insulin. The synthetic peptides B1-8, B9-30, and B1-30 reacted with antiserum to natural B-chain but high levels of peptides (B2-8)2, B9-14, and (B17-23)2 were inactive. The symmetrical double peptide (B1-8)2 reacted with guinea pig antiserum to intact insulin as well as with antiserum to B-chain and certain sera from insulin-resistant diabetic patients. The results indicated that injection of ox insulin into guinea pigs caused production of anaphylactic anti-bodies mainly towards antigenic loci in the regions A10-21 and B1-8 of the insulin molecule, whereas antigenic determinants in the regions A1-9 and B24-30 were less important.