The Immune Response to GHRH, Relationship to Conformation

Summary

Antibodies to GHRH_1-44, GHRH_1-29, and proinsulin were induced in guinea pigs. GHRH_1-44 forms 7 S and 10 S complexes with antibodies. It is a divalent antigen. The sequence 30-44 bound 85% of the antibodies to GHRH_1-44 with high affinity (3.8 ± 0.9 × 10⁹ l/mol). The fragment 1-29 bound with low affinity (0.6 ± 0.3 × 10⁹ l/mol) 15% of the antibodies (2p < 0.001). Antibodies to GHRH_1-29 had low affinity towards the native hormone (0.4 ± 0.2 × 10⁹ l/mol) and the region 1-29 (0.3 ± 0.2 × 10⁹ l/mol). Antibodies to proinsulin bound linear C-peptide with lower affinity (0.3 ± 0.2 × 10⁹ l/mol) than the C-peptide loop in proinsulin (3.4 ± 0.9 × 10⁹ l/mol). It is concluded that the conformation of the epitopes on the sequence 1-29, recognized during the immune response, i. e. on the cell membrane, is different from the conformation of GHRH_1-29 or GHRH_1-44 in aqueous solution.

Key words

GHRH Antibodies - GHRH Conformation - GHRH_1-29 - C-peptide