A sensitive enzyme immunoassay for anti-thyroglobulin antibody using Fab'-horseradish peroxidase conjugate. Evaluation of in vitro anti-thyroglobulin antibody synthesis by lymphocytes from patients with autoimmune thyroid disease.

A sensitive enzyme immunoassay (EIA) for the detection of anti-thyroglobulin (Tg) antibodies was developed using Fab'-horseradish peroxidase (HRP) conjugate. Anti-Tg antibody was assayed by incubation with a thyroglobulin-coated polystyrene ball and then with affinity-purified anti-IgG Fab'-HRP conjugate. The HRP activity was assayed fluorimetrically. The sensitivity was 625 amol/tube and anti-Tg antibody levels between 0.5 and 200 ng/ml could be determined. The recoveries of anti-Tg antibody added to human sera at three different concentrations were 94.2-101.0%. Both within- and between-assay coefficients of variation were below 10%. Significant correlation was observed between values by the EIA and TGHA method (Kendall's rank correlation coefficient = 0.712, P less than 0.001). The present EIA for anti-Tg antibody is sensitive enough to determine anti-Tg antibody synthesized in vitro by the lymphocytes from patients with autoimmune thyroid disease and normal subjects. The amounts of anti-Tg antibody synthesized by peripheral lymphocytes from patients with Hashimoto's disease were significantly greater than those from patients with Graves' disease, although serum levels of anti-Tg antibody were usually elevated in both groups of patients. The results obtained suggest that anti-Tg antibody is synthesized in a different manner in patients with Hashimoto's disease and in patients with Graves' disease.