Quantitative reverse transcription-PCR measurement of thyroglobulin mRNA in peripheral blood of healthy subjects.

BACKGROUND: Thyroglobulin mRNA can be detected qualitatively in the peripheral blood of patients with metastatic thyroid cancer, thyroid cancer patients with residual thyroid bed uptake, and individuals with no known thyroid disease with intact thyroid glands by use of a lengthy, highly sensitive extraction technique. To improve and broaden the clinical usefulness of this assay, we developed a quantitative reverse transcription (RT)-PCR assay for thyroglobulin mRNA, using RNA recovered from whole blood with a simplified extraction technique. METHODS: Whole blood was drawn from 32 healthy subjects in standard EDTA blood collection tubes. Total RNA was extracted from whole blood, using the PUREscript RNA Isolation Kit. RT-PCR using intron-spanning primers was used to quantitatively amplify thyroglobulin mRNA, using the ABI PRISM 7700 Sequence Detection System with a fluorescent-labeled, thyroglobulin-specific oligonucleotide probe. Thyroid RNA calibration curves were created using total RNA recovered from a single nondiseased thyroid gland. RESULTS: Qualitative RT-PCR demonstrated the presence of thyroglobulin mRNA in the whole blood sample of each healthy subject. The mean concentration of thyroglobulin mRNA detected in these subjects was 433 +/- 69 ng of total thyroid RNA per liter of whole blood (range, 26-1502 ng/L). Overall assay imprecision (CV) was 24% for five samples analyzed 10 times each in separate analytical runs on different days. CONCLUSIONS: Thyroglobulin mRNA can be accurately detected and quantified in peripheral blood from healthy subjects. This new quantitative technique may improve the clinical utility of circulating thyroglobulin mRNA detection in patients with thyroid disease.

The influence of triiodothyronine, thyroxine, thyrotropin, and methimazole on thyroid cell MHC class II antigen expression.

We have studied the influence of triiodothyronine (T3), thyroxine (T4), thyrotropin (TSH), and methimazole (MMI) on the expression of major histocompatibility (MHC) Class II antigen expression in human thyroid cells. T3, T4, TSH, and MMI in various combinations were added together with interferon-gamma (IFN-gamma) to human thyrocytes or to cultured FRTL-5 cells. Neither T3 nor T4, alone, caused inhibition of the IFN-gamma stimulation of thyrocyte HLA-DR expression. Moreover, the combination of both drugs at various concentrations did not inhibit this expression except only in low ranges (T3 at 0.3 nmol/liter and T4 at 12.9 nmol/liter). MMI only at a concentration of 3.0 mmol/liter caused significant inhibition of IFN-gamma-induced HLA-DR expression. However, the addition of T3 (range, 0.3-9.2 nmol/liter) or T4 (12.9-129.0 nmol/liter) prevented the MMI-induced inhibition. This phenomenon may be explained by the action of MMI on inhibiting the synthesis of T3 and T4. At a concentration of 100 microU/ml, TSH enhanced IFN-gamma-induced HLA-DR expression. It is possible that TSH induced the expression of large numbers of IFN-gamma receptors, thereby enhancing the production of HLA-DR in response to IFN-gamma. Our studies suggest that MMI does not alter thyrocyte HLA-DR expression in vitro, especially when combined with T3 or T4; however, MMI may still induce or perpetuate immune effects in vivo secondary to its influence on thyroid hormone production or thyroid antigen presentation.