Detection of IL-12, IL-13, and IL-15 messenger ribonucleic acid in the thyroid of patients with autoimmune thyroid disease

IL-12, IL-13, and IL-15 are important cytokines that have not been studied previously in human autoimmune thyroid diseases. By applying RT-PCR on RNA extracted from tissue samples, we have investigated in vivo gene expression of these cytokines in multinodular goiter (MNG), Graves' disease (GD), and Hashimoto's thyroiditis (HT). In addition, in vitro studies were carried out using the transformed human thyroid cell line, HT-ori3, and primary thyroid cell cultures derived from patients with GD. These cells were used either unstimulated or stimulated for 12 h with TSH, IL-1, or interferon-gamma (IFN-gamma). IL-12 p40 gene expression was identified in 2 of 10 MG samples, 6 of 12 GD, and 3 of 4 HT. HT-ori3 and primary thyroid cell cultures were positive for IL-12 p40 messenger RNA (mRNA) expression in both unstimulated and stimulated cell cultures. IL-13 mRNA was expressed in 2 MNG, 9 GD, and 1 HT sample. Both HT-ori3 and primary thyroid cultures expressed IL-13 after TSH, IL-1, or IFN-gamma stimulation; unstimulated primary cultures of thyroid cells, however, did not express IL-13. IL-15 gene expression was detected in 8 MNG, 8 GD, and 4 HT samples. HT-ori3 and primary thyroid cell cultures, stimulated with TSH, IL-1, or IFN-gamma, showed expression of this cytokine. Unstimulated cells showed only a weak expression. Our results indicate that the cytokine patterns in the various diseases studied are heterogeneous; that thyroid cells can express IL-12, IL-13, and IL-15 mRNA in culture, particularly after TSH, IL-1, or IFN-gamma stimulation; and that IL-15 is expressed in most of the tissue samples studied.