ABSTRACT
Objective To study the antigenicity of human thyrotropin receptor(hTSHR)amino terminus (amino acid 29～280)and its association with Graves' disease.Methods Total thyroid RNA was prepared from human normal thyroid tissue.RNA was then reversely transcripted and cDNA was subjected to PCR amplification.PCR product was cloned into pcDNA3.1 and the recombinant plasmid was named pcDNA3.1/hTSHR188～940bp. Balb/c mice were immunized with peDNA3.1/hTSHR188～940bp. The levels of serum thyroxin,anti-TSHR antibody(TRAb)and thyroid stimulating antibody(TSAb)were measured,and the pathological changes of thyroid tissue were also observed.Results A 753 bp fragment encoding hTSHR ectodomain amino end was obtained after PCR amplification.Confirmed by Hind Ⅲ restriction enzyme digestion and DNA sequencing,pcDNA3.1/hTSHR188～940bphad been constructed successfully,with the correct sequence and direction of hTSHR188～940bp.In the Balb/c mice treated with pcDNA3.1/hTSHR188～940bp,elevated TRAb in week 6(0.148±0.018)were observed compared with those at week o(0.106±0.006,P＜0.01),and kept a higher level till week 10(0.134±0.011,P＜0.01).T4 and TSAb index values were significantly increased in week 10.Serum T4 concentration increased from(41.02±7.97)μg/L in week 0 to(62.20±12.77)μg/L in week 10(P＜0.01);TSAb index values rose from 0.864±0.076 at week 0 to 1.392±0.615(P＜0.01).Thyroid pathological examination showed that proliferated thyroid follicular epithelial cells and foll icular eapacity increased.Inflammatory cells were occasionally found.Conclusions There are antigen epitopes in hTSHR ectodomain amino acid 29～280,which can stimulate the production of TSAb.And the latter induces hyperthyroidism and Graves' disease like manifestations.It suggests that hTSHR ectodomain amino acid 29～280 is closely associated with Graves' disease,and maybe one of important etiological factors leading to the disease.