Iodine content of thyroglobulin in NOD.H2h4 mice developing iodine-accelerated autoimmune thyroiditis

Abstract

oBJective: In NOD.H2 h4 mice, high dietary iodine intake has been known to cause Iodineaccelerated spontaneous Autoimmune thyroiditis (IsAt) via an unknown mechanism. the aim of the study was to examine whether the NOD.H2 h4 genetic background predisposes to enhanced iodine organification in thyroglobulin (tg), a target autoantigen in IsAt. DEsIGN: to avoid issues associated with an ongoing anti-tg antibody response, we assessed tg iodination levels in iodine-fed, b-cell deficient NOD.H2 h4 mice. Additionally, we tested whether humoral or cellular immune responses of iodine-fed NOD.H2 h4 mice are preferentially directed to tg with increased iodine content (I-tg) or known pathogenic tg peptides that contained iodine. rEsULts: the iodine content of tg was not significantly different between control (9.0±2.7 I atoms per monomer) and iodine-fed mice (10.9±0.3 I atoms per monomer). Furthermore, in iodine-fed NOD.H2 h4 mice developing IsAt, strong but equivalent serum IgG responses were detected to both tg or I-tg, whereas their lymphoid cells were stimulated weakly but equally well by tg or I-tg in vitro and did not show reactivity against a panel of five pathogenic tg peptides that contained iodine. cONcLUsIONs: the results suggest that development of IsAt in NOD.H2 h4 mice is not associated with enhanced iodine organification or differential b-or t-cell responses to iodinated determinants in tg.

The Thyroxine-Containing Thyroglobulin Peptide (aa 2549–2560) Is a Target Epitope in Iodide-Accelerated Spontaneous Autoimmune Thyroiditis

“…In this model, addition of 0.05% NaI in the drinking water has been found to accelerate both the incidence and the severity of SAT (1-4, 7-10), providing opportunities to study the interplay of genetics and environment in the progression of autoimmune disease. Iodide-accelerated spontaneous autoimmune thyroiditis (ISAT) is characterized by mononuclear cell infiltration of the thyroid and strong serum IgM and IgG responses to thyroglobulin (Tg) (3,4,(7)(8)(9)(10). Immunohistochemical staining studies have suggested that the thyroid is initially infiltrated by CD4 + and CD8 + cells (11)(12)(13), and depletion experiments have shown that CD4 + cells are required for the development and maintenance of ISAT (3,4).…”

“…Immunohistochemical staining studies have suggested that the thyroid is initially infiltrated by CD4 + and CD8 + cells (11)(12)(13), and depletion experiments have shown that CD4 + cells are required for the development and maintenance of ISAT (3,4). Weak proliferative responses of thyroid-draining cervical lymph node cells (cLNCs) to Tg have been observed at various time points after the initiation of the NaI diet regimen (10) (14). In NOD.H2 h4 mice developing ISAT, we have not been previously able to detect proliferative splenic cell responses to several A k -restricted pathogenic T cell epitopes, 56 d following the initiation of iodide supplementation (10).…”

“…Weak proliferative responses of thyroid-draining cervical lymph node cells (cLNCs) to Tg have been observed at various time points after the initiation of the NaI diet regimen (10) (14). In NOD.H2 h4 mice developing ISAT, we have not been previously able to detect proliferative splenic cell responses to several A k -restricted pathogenic T cell epitopes, 56 d following the initiation of iodide supplementation (10). To address the concern that thyroid Ag-specific T cells may not be detected in the periphery during later stages of the disease because they might have already migrated into the thyroid, we have in this study examined Ag-specific responses of cLNCs in the initial stages of ISAT and of intrathyroidal lymphocytes during the course of the disease.…”

“…Tg was purified from thyroid glands of female CD-1 mice (Charles River, Quebec, QC, Canada) after centrifugation of thyroid extract at 16,000 3 g, followed by passage through a Sepharose CL-4B column (Amersham Biosciences, Uppsala, Sweden), as previously described (10). F-moc L-thyroxine was produced as previously described (18,19).…”

Molecular parameters linking thyroglobulin iodination with autoimmune thyroiditis

“…5,6 However, the genetic background of this strain does not promote generation of I-Tg in vivo, and there is no evidence for differential B-cell or T-cell responses to Tg vs I-Tg in iodide-fed NOD.H-2h4 mice developing accelerated SAT. 57 Indeed, in vivo formation of I-Tg in normal (i.e. non-goitrous) mice exposed to a chronic iodide-rich diet has not yet been reported.…”