Biological activities of rat antisera raised against synthetic peptides of human thyrotropin receptor.

Twenty three male Wistar rats were divided into five groups and were immunized with five overlapping synthetic peptides (Group I (n = 5), peptide 12-30; Group II (n = 5), 24-44; Group III (n = 4), 308-328; Group IV (n = 5), 324-344; and Group V (n = 4), 339-364) of human thyrotropin receptor (TSHR), which had been conjugated with rabbit serum albumin. Sera obtained 34 days after the first immunization were investigated for their ability to displace 125I-TSH binding to thyrotropin receptor (thyrotropin binding inhibitor immunoglobulins (TBII)). In addition, biological activity, namely thyroid stimulating (TSAb) or blocking (TSBAb) activities in them were tested with cultured porcine thyroid cells. TBII activities in Group I, II, III, IV, and V rats were 12.6 +/- 4.1% (range 9.2-17.2%), 16.3 +/- 4.0% (range 11.7-22.0%), 16.7 +/- 4.9% (range 13.2-20.1%), 14.5 +/- 5.7% (range 8.1-19.0%), and 13.8 +/- 6.3% (range 8.1-14.3%), respectively, which were not significantly different from control rat sera (12.3 +/- 6.7%, range 1.2-20.1%). TSAb activities in Group I, II, III, IV, and V rats were 608 +/- 675% (range 275-1813%), 234 +/- 26% (range 209-265%), 313 +/- 175% (range 187-568%), 190 +/- 63% (range 145-301%), and 134 +/- 24% (range 107-158%), respectively. TSAb activities in Group I, II, III, and IV rats were significantly higher than those from control rat sera (P < 0.01) while those of Group V were not significantly different from control rat sera. None of the rats in each group exhibited TSBAb activity.(ABSTRACT TRUNCATED AT 250 WORDS)