Autoimmune thyroid disease--Hashimoto thyroiditis and Graves' disease--patients produce high levels of thyroid autoantibodies and contain lymphoid tissue that resembles secondary lymphoid follicles (LFs). We compared the specificity, structure, and function of tonsil and lymph node LFs with those of the intrathyroidal LFs to assess the latter's capability to contribute to autoimmune response. Thyroglobulin and thyroperoxidase binding to LFs indicated that most intrathyroidal LFs were committed to response to thyroid self-antigens and were associated to higher levels of antibodies to thyroglobulin, thyroperoxidase, and thyroid-stimulating hormone receptor. Intrathyroidal LFs were microanatomically very similar to canonical LFs, ie, they had well-developed germinal centers with mantle, light, and dark zones and each of these zones contained B and T lymphocytes, follicular dendritic and interdigitating dendritic cells with typical phenotypes. Careful assessment of proliferation (Ki67) and apoptosis (terminal dUTP nick-end labeling) indicators and of the occurrence of secondary immunoglobulin gene rearrangements (RAG1 and RAG2) confirmed the parallelism. Unexpected high levels of RAG expression suggested that receptor revision occurs in intrathyroidal LFs and may contribute to generate high-affinity thyroid autoantibodies. Well-formed high endothelial venules and a congruent pattern of adhesion molecules and chemokine expression in intrathyroidal LFs were also detected. These data suggest that ectopic intrathyroidal LFs contain all of the elements needed to drive the autoimmune response and also that their microenvironment may favor the expansion and perpetuation of autoimmune response.

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Thyroid Autoimmune Disease: Demonstration of Thyroid Antigen-Specific B Cells and Recombination-Activating Gene Expression in Chemokine-Containing Active Intrathyroidal Germinal Centers

Autoimmune diseases have a high prevalence in the population and autoimmune thyroid disease (AITD) is one of the most common representatives. Thyroid autoantibodies are frequently detected in patients with AITD but also in subjects without manifest thyroid dysfunction. The high prevalence raises questions regarding a potential role in extra-thyroidal diseases. This review summarizes the etiology and mechanism of AITD and addresses prevalence of antibodies against thyroperoxidase, thyroid stimulating hormone receptor and anti-thyroglobulin and their action outside the thyroid. The main issues limiting the reliability of the conclusions drawn here include problems with different specificities and sensitivities of the antibody detection assays employed, as well as potential confounding effects of altered thyroid hormone levels, and lack of prospective studies. In addition to the well-known effects of thyroid stimulating hormone receptor antibodies on fibroblasts in Graves’ disease, studies speculate on a role of anti-thyroid antibodies in cancer. All antibodies may have a tumor-promoting role in breast cancer carcinogenesis despite anti-thyroperoxidase antibodies having a positive prognostic effect in patients with overt disease. Cross-reactivity with lactoperoxidase leading to induction of chronic inflammation might promote breast cancer, while anti-thyroid antibodies in manifest breast cancer might be an indication for a more active immune system. A better general health condition in older women with anti-thyroperoxidase antibodies might support this hypothesis. The different actions of the anti-thyroid antibodies correspond to differences in cellular location of the antigens, titers of the circulating antibodies, duration of antibody exposure, and immunological mechanisms in Graves’ disease and Hashimoto’s thyroiditis.

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Thyroid Autoimmunity: Role of Anti-thyroid Antibodies in Thyroid and Extra-Thyroidal Diseases

Autoimmune thyroid disease is common and was the first autoimmune disease to be described, based on observations in animals immunized with thyroid extract and adjuvant. There are several different clinical presentations which, although being distinctive, share some common features in terms of genetic susceptibility, environmental factors that predispose to disease and pathogenic features such as the presence of autoantibodies against thyroglobulin and thyroid peroxidase. In autoimmune hypothyroidism, the thyroid is initially enlarged due to the presence of a marked lymphocytic infiltrate; this phase is followed by fibrosis, atrophy of the gland, and failure to synthesize normal levels of thyroid hormones. The main etiological factors in this process are cytotoxic T cells and an intrathyroidal proinflammatory state created by local cytokine release. Humoral autoimmunity may contribute through the action of thyroid-stimulating hormone (TSH) receptor-blocking autoantibodies or through the activation of complement and antibody-dependent NK cell-mediated cytotoxicity. In Graves' disease, thyroid overactivity is caused by autoantibodies which stimulate the TSH receptor. T cells which recognize the receptor also localize to the orbit in many of these patients, as a subpopulation of fibroblasts at this location also express the receptor; the cytokines produced by these T cells in turn leads to the clinical features of Graves' ophthalmopathy.

Autoimmune Thyroid Disease

Context: Thyroglobulin autoantibodies (TgAb) are primarily measured in serum in conjunction with thyroglobulin (Tg)—the primary tumor marker used to monitor patients with differentiated thyroid cancers (DTC). Every specimen needs TgAb testing to authenticate that the Tg measurement is not compromised by TgAb interference. When present, TgAb concentrations per se can be monitored as a surrogate tumor marker. Objectives: The aims of the study were: 1) to review published reports concerning whether there are associations between DTC, thyroid autoimmunity (Hashimoto's thyroiditis), and the presence of TgAb; and 2) to evaluate the methodological factors that influence TgAb interference with serum Tg testing. Data Sources: PubMed was used to identify studies published over the last 55 yr that focused on DTC relationships with thyroid autoimmunity and the presence of thyroid autoantibodies. Results: Many studies have reported significant associations between papillary thyroid cancer and Hashimoto's thyroiditis t...

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Clinical Utility of Thyroglobulin Antibody (TgAb) Measurements for Patients with Differentiated Thyroid Cancers (DTC)

Measurement of serum thyroglobulin is primarily used as a tumor marker in the postoperative management of patients with differentiated thyroid cancer. Unfortunately, the technical quality of current thyroglobulin assay methods varies and influences the clinical utility of this test. Two different methodologic approaches are used to measure serum thyroglobulin: the original competitive radioimmunoassay methodology and noncompetitive immunometric assay methods. Although the newer immunometric assays offer the technical benefits of eliminating the use of isotopes, using smaller specimen volumes, and having higher sensitivity potential, shorter turnaround times and the convenience of automation, immunometric assays also have a higher propensity for interference from both thyroglobulin autoantibodies and heterophilic antibodies, if present in the specimen. It is critical that physicians understand the technical limitations inherent in thyroglobulin measurement in order to effectively use this test for the postoperative management of patients with differentiated thyroid cancers.

Measuring thyroglobulin and thyroglobulin autoantibody in patients with differentiated thyroid cancer.

A panel of human monoclonal thyroglobulin (Tg) autoantibodies (TgAAb) has been used to analyze autoantigenic determinants on human Tg and to investigate the relationship between variable (V) region gene sequences and epitope specificity Two monoclonal TgAAb bound to the same (or closely related) epitope on Tg, and these were defined as type I TgAAb Three other monoclonals bound to a different site and were defined as type II TgAAb Inhibition studies with mixtures of type I and type II monoclonal TgAAb (Fab)2 preparations indicated that a mixture of the (Fab)2s almost completely inhibited (> 75%) labeled Tg binding to intact TgAAb in the sera of apparently healthy blood donors and patients with autoimmune thyroid disease (AITD) Type I TgAAb predominated in apparently healthy blood donors' sera, whereas type II TgAAb predominated in AITD sera Analysis of V region gene sequences of the TgAAb indicated that a range of light chain and heavy chain genes from different gene families was used Furthermore, the same germline genes that are used by TgAAb are also well represented in the genes coding for other self- and nonself-reactive antibodies No homology in terms of light chain and heavy chain gene families, germline gene usage, or complementarity determining region sequences was observed in TgAAb directed to the same or closely related epitopes Our studies show that TgAAb are directed to two major conformational epitopes on the Tg molecule and that the proportion of TgAAb directed to these epitopes in apparently healthy blood donors and that in patients with AITD appear to be different TgAAb derived from different germline genes and with different complementarity determining region sequences can display similar epitope specificity, and this indicates that AAb directed to the same or a closely related epitope show considerable heterogeneity at the molecular level

C Pegg

Papers

Monoclonal thyroglobulin autoantibodies: variable region analysis and epitope recognition.