ETA2023 Poster Presentations Basic Thyroid Gland, Iodine & Autoimmunity Basic (9 abstracts)
Characterization of anti-thyroglobulin antibodies epitopes in patients with hashimoto’s thyroiditis in areas with normal and excessive iodine intake
Mauro Casula1, Nicola Viola1, Benedetta Migliorucci1, Yuji Nagayama2, Ichiro Horie3, Atsushi Kawakami3, Hiraku Kameda4, Akinobu Nakamura5, Tatsuya Atsumi4, Hiraku Kameda6, Alessandro Brancatella1, Daniele Sgrò1, Laura Tosatto7, Ferruccio Santini1, Francesca Coscia7 & Francesco Latrofa1
1University of Pisa, Department of Clinical and Experimental Medicine, Pisa, Italy; 2Nagasaki University, Department of Molecular Medicine, Nagasaki, Japan; 3Nagasaki University Graduate School of Biomedical Sciences, Department of Endocrinology and Metabolism, Division of Advanced Preventive Medical Sciences, Nagasaki, Japan; 4Hokkaido University, Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Sapporo, Japan; 5Hokkaido University, Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Sapporo, Japan; 6Sapporo Diabetes and Thyroid Clinic, Sapporo, Japan; 7Human Technopole, Structural Biology Research Centre, Milan, Italy
Introduction: An increase in dietary iodine uptake, from insufficient to borderline values, induces the unmasking of a hidden epitope on thyroglobulin (Tg). No data about the effect of an excessive iodine intake on the expression of Tg epitopes recognized by human TgAb are available.
Objective: To compare the expression of TgAb epitopes in sera of Hashimoto’s thyroiditis (HT) patients from areas with adequate, slightly and markedly excessive iodine intake.
Methods: Inhibition of Tg-TgAb binding was evaluated in HT patients from Italy (Ita, n. 12), Nagasaki (Nag, n. 11) and Sapporo (Sap, n. 11). Median urinary iodine in these cohorts is 124, 363 and 1015 μg/l. Tg-TgAb binding was inhibited by 4 recombinant human Tg-Ab Fabs that recognize Tg epitopes A, B, C and D. The ability of each AbTg-Fab to inhibit Tg-TgAb binding was evaluated by an immunoenzymatic method. 50 μl/well of TgAb-Fab (or culture medium) was incubated with 50 μl of serum (diluted to provide a final OD of ~ 1.0). The inhibition by TgAb-Fab was calculated from the OD values for serum TgAb alone - serum TgAb + TgAb-Fab and expressed as a percentage of serum TgAb alone.
Results: Levels of inhibition were similar for TgAb-Fab A (Ita: 47 ± 9%; Nag: 41 ± 11%; Sap: 32 ± 10%, P = 0.095) and TgAb-Fab B (Ita: 31 ± 11%; Nag: 36 ± 11%; Sap 37 ± 7%; P = 0.561), different for TgAb-Fab C (Ita 26 ± 5%; Nag: 40± 12%; Sap 31 ± 7%; P = 0.015) and TgAb-Fab D (Ita: 24 ± 7%; Nag 34 ± 8%; Sap 31 ± 10%; P = 0.025, Kruskal-Wallis). In pairwise comparison, the level of inhibition was lower in Ita sera by TgAb-Fab C (P = 0.009 vs Nag) (P = 0.037 vs Sap) and by TgAb-Fab D (P = 0.027 vs Nag) (P = 0.017 vs Sap, Mann-Whitney).
Conclusions: Levels of TgAb of HT patients are higher in areas with excessive iodine intake. We have previously shown that a rise in urinary iodine from 86.5 to 112.5 μg/l induced the unmasking of epitope B on Tg. A further increase (up to 363 μg/l) induces a higher expression of epitopes C and D. An additional increase (up to 1015 μg/l) does not lead to a different recognition of the 4 epitopes. Likely, other epitopes, in addition to the 4 identified by our TgAb-Fabs, are recognized by TgAb from Japanese HT patients.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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