Development of chicken antibodies toward the human thyrotropin receptor peptides and their bioactivities

We have synthesized four peptides (P2, P4, E3 and P1) corresponding to different segments of human thyrotropin (TSH) receptor. We have obtained antibodies by immunizing them to chickens, and antibodies are evaluated for their thyroid stimulating antibody (TSAb), thyroid stimulation blocking antibody (TSBAb) and TSH-binding inhibitor immunoglobulin (TBII) activities. None of the antibodies had TSAb activity. Antibodies against human TSH receptor specific region such as P2 and P4 (P2: No. 372-397, P4: No. 341-358) had TSBAb and TBII activities. Anti-E3 antibody (E3: the third putative extracellular loop, No. 649-661) had only TSBAb activity. Anti-P1 antibody (P1: high homology with pig LH/CG receptor, No. 398-417), however, had none. These results suggest that anti-TSH receptor antibodies to different antigenic epitopes show heterogeneity in their biological activities.