Tonacchera M, Agretti P, Ceccarini G, Lenza R, Refetoff S, Santini F, Pinchera A, Chiovato L, Vitti P
Dipartimento di Endocrinologia e Metabolismo, Medicina del Lavoro, Università di Pisa, Pisa, Italy.
Eur J Endocrinol. 2001 Jun;144(6):611-8. doi: 10.1530/eje.0.1440611.
The human sodium iodide symporter (hNIS) is a candidate autoantigen in autoimmune thyroid diseases. To investigate the possible existence of autoantibodies able to interfere with the biological activity of hNIS, an assay was developed using a cell line stably expressing hNIS.
hNIS complementary cDNA cloned in pcDNA3 and a neomycin resistance gene vector were co-transfected into CHO cells. After selection with geneticin, a cell line termed PA4, showing the highest level of Na(125)I uptake, was characterized. The time course of iodide uptake was evaluated by incubating PA(4) cells with 10 micromol/l NaI and 0.1 microCi Na(125)I for a period up to 90 min. The accumulation of iodide increased linearly between 2 and 10 min, reaching a plateau at 45 min. The curve of iodide efflux mirrored that of iodide influx. Both perchlorate and thiocyanate inhibited iodide uptake in PA(4) cells in a dose-dependent manner starting from concentrations as low as 0.01 and 0.1 micromol/l respectively and complete inhibition was obtained at concentrations of 100 micromol/l perchlorate and 1000 micromol/l thiocyanate. The sensitivity of the inhibition assay was further improved using both inhibitors after 5 min incubation and in the absence of cold NaI.
Included in the study were 42 patients with Graves' disease (25 had active hyperthyroidism, ten were euthyroid and seven had hypothyroidism); 34 patients with Hashimoto's thyroiditis (one was euthyroid, four had subclinical hypothyroidism and 29 were overtly hypothyroid); and 19 with atrophic thyroiditis (all hypothyroid). Four out of eight whole sera from patients with Hashimoto's thyroiditis, and 8 out of 25 whole sera from patients with Graves' disease caused an inhibition of iodide uptake in PA(4) cells greater than 20% but also in 4 out of 15 sera from normal subjects. This inhibition activity exerted by sera from patients and controls was lost after dialyzing against buffer. Accordingly, IgGs purified from sera of all patients with Graves' disease and with Hashimoto's thyroiditis or atrophic thyroiditis were devoid of any effect on iodide uptake.
In conclusion, we believe that autoantibodies able to block the function of hNIS are very rare.
人钠碘同向转运体（hNIS）是自身免疫性甲状腺疾病中的候选自身抗原。为研究是否存在能够干扰hNIS生物活性的自身抗体，利用稳定表达hNIS的细胞系开展了一项检测。
将克隆于pcDNA3的hNIS互补DNA与新霉素抗性基因载体共转染至CHO细胞。经遗传霉素筛选后，鉴定出一个名为PA4的细胞系，其显示出最高水平的Na(125)I摄取。通过将PA(4)细胞与10 μmol/L NaI和0.1 μCi Na(125)I孵育长达90分钟来评估碘摄取的时间进程。碘的积累在2至10分钟之间呈线性增加，在45分钟时达到平台期。碘流出曲线与碘流入曲线相似。高氯酸盐和硫氰酸盐均以剂量依赖方式抑制PA(4)细胞中的碘摄取，分别从低至0.01和0.1 μmol/L的浓度开始，在100 μmol/L高氯酸盐和1000 μmol/L硫氰酸盐的浓度下获得完全抑制作用。在5分钟孵育后且不存在冷NaI的情况下，使用两种抑制剂进一步提高了抑制检测的灵敏度。
研究纳入了42例格雷夫斯病患者（25例有活动性甲亢，10例甲状腺功能正常，7例有甲减）；34例桥本甲状腺炎患者（1例甲状腺功能正常，4例有亚临床甲减，29例有明显甲减）；以及19例萎缩性甲状腺炎患者（均为甲减）。桥本甲状腺炎患者的8份全血清中有4份，格雷夫斯病患者的25份全血清中有8份导致PA(4)细胞中的碘摄取抑制大于20%，但正常受试者的15份血清中有4份也出现这种情况。患者和对照血清所发挥的这种抑制活性在与缓冲液透析后丧失。因此，从所有格雷夫斯病、桥本甲状腺炎或萎缩性甲状腺炎患者血清中纯化的IgG对碘摄取均无任何影响。
总之，我们认为能够阻断hNIS功能的自身抗体非常罕见。
