Schwarz-Lauer L, Chazenbalk G D, Mclachlan S M, Ochi Y, Nagayama Y, Rapoport B
Autoimmune Disease Unit, Cedars-Sinai Research Institute, Los Angeles, California 90048, USA.
Thyroid. 2002 Feb;12(2):115-20. doi: 10.1089/105072502753522347.
Recently, many exceptions have been reported that undermine the concept that the epitopes for thyroid-stimulating autoantibodies (TSAb) and thyrotropin-blocking autoantibodies (TBAb) lie within the N-terminal and C-terminal portions of the thyrotropin receptor (TSHR) ectodomain, respectively. Here we have used a new approach to examine the issue by attempting to neutralize autoantibodies with the purified, N-terminal 289 amino acids of the TSHR ectodomain (TSHR-289), essentially the A subunit. Immunoglobulin G (IgG) with TSAb activity from 10 patients with Graves' disease was preincubated with or without purified active or inactive TSHR-289. Active, but not inactive, TSHR-289 completely neutralized TSAb activity in all sera. We then tested the ability of active TSHR-289 to neutralize TBAb activity in two rare hypothyroid patients with pure TBAb activity lacking agonist activity. IgG from both patients was extremely potent in the TBAb assay. Unlike with TSAb, preincubation of the IgG with a large excess of active TSHR-289 (20 microg/mL) revealed a remarkable divergence. TBAb activity from one patient was totally neutralized whereas in the other patient TBAb activity was totally unaffected. In conclusion, using a new approach, we confirm that the major portion of the TSAb epitope in the 418 amino acid ectodomain lies upstream of residue 289 (within the A subunit). In contrast, TBAb that cause hyperthyroidism can be more heterogeneous, with epitopes that lie largely upstream (A subunit) or downstream (B subunit) of residue 289.
最近，有许多例外情况被报道，这些例外削弱了甲状腺刺激自身抗体（TSAb）和促甲状腺素阻断自身抗体（TBAb）的表位分别位于促甲状腺素受体（TSHR）胞外域的N端和C端部分这一概念。在此，我们采用了一种新方法来研究该问题，即尝试用纯化的TSHR胞外域N端289个氨基酸（TSHR - 289，本质上是A亚基）来中和自身抗体。将来自10例格雷夫斯病患者的具有TSAb活性的免疫球蛋白G（IgG）与纯化的活性或非活性TSHR - 289进行预孵育或不进行预孵育。活性而非非活性的TSHR - 289完全中和了所有血清中的TSAb活性。然后，我们测试了活性TSHR - 289在两名罕见的仅有TBAb活性而缺乏激动剂活性的甲状腺功能减退患者中中和TBAb活性的能力。两名患者的IgG在TBAb检测中都极具效力。与TSAb不同，将IgG与大量过量的活性TSHR - 289（20μg/mL）预孵育显示出显著差异。一名患者的TBAb活性被完全中和，而另一名患者的TBAb活性则完全未受影响。总之，通过一种新方法，我们证实了在418个氨基酸的胞外域中，TSAb表位的主要部分位于第289位残基的上游（在A亚基内）。相比之下，导致甲状腺功能亢进的TBAb可能更具异质性，其表位很大程度上位于第289位残基的上游（A亚基）或下游（B亚基）。
