IgG subclass distribution of thyroglobulin antibodies in patients with thyroid disease

Abstract

SUMMARYThe IgG subclass distribution of thyroglobulin antibodies (TgAb) has been studied in Hashimoto and Graves' patients by several investigators with conflicting results, in part explainable by methodological problems. We have recently developed a quantitative ELISA to measure in absolute terms the serum concentration of TgAb subclasses. The aim of the present study was to apply this method in a large series of patients with autoimmune as well as, for the first time, non-autoimmune thyroid diseases. We examined 28 patients with Hashimoto's thyroiditis, 30 with Graves' disease, 21 with thyroid carcinoma and 18 with non-toxic goitre, all selected for the presence of TgAbs. The results indicated that TgAbs in thyroid diseases were not restricted to any particular isotype, but comprised all four IgG subclasses. IgGI was represented similarly in the four groups. The same was true for IgG3, even though its contribution to the total antibody content was very small. IgG4 was the dominant subclass in patients with Graves' disease, thyroid carcinoma and non-toxic goitre, probably reflecting a prolonged antigenic challenge. In Hashimoto's thyroiditis IgG2 was dominant, possibly because T helper lymphocytes infiltrating the thyroid are typically Thl type.

In vitro assays to test the interference of anti-thyroglobulin antibodies on thyroglobulin measurement

“…In fact, sera from all six cases considered ambiguous by the UNICAP method, among which were the two negative cases by the IMMULITE method, were shown to interfere with the Tg measurement. This observation reinforces the fact that assays for TgAb measurements have different sensitivities and even low concentrations of TgAb, which may not be detected by some methods, can interfere with Tg measurements as previously reported [1,13,23,34,35]. Thus, in doubtful cases of undetectable Tg, it might be There is a trend for a higher interference in association with a higher concentration of TgAb but this is not a rule.…”

IgG4-related Ocular Adnexal Disease Mimicking Thyroid-associated Orbitopathy

“…The TPOAb in the sera of patients with HT are predominantly associated with IgG1 (22). In contrast, IgG2 is the dominant subtype of TgAb in patients with HT (23). Antigen presentation on the surface of HLA-DR molecules plays an important role in autoimmunity.…”

The presence of thyroid peroxidase antibody of IgG2 subclass is a risk factor for thyroid dysfunction in chronic hepatitis C patients

“…IgG1 is important during inflammation (36) and presents regardless of thyroid function (37). Higher IgG4 levels are detectable with prolonged immune response during injury (38).…”