Analysis of regulatory T cells frequency in peripheral blood and tumor tissues in papillary thyroid carcinoma with and without Hashimoto's thyroiditis

Regulatory T cells (Treg) suppress the immune reaction. The aim of the present study was to investigate the clinicopathologic significance and roles of Treg in papillary thyroid carcinoma (PTC) patients with and without Hashimoto's thyroiditis. Flow cytometry was used to detect the percentage of CD4+CD25+CD127low/- Treg among CD4+ T cells in peripheral blood. FoxP3+ Treg were detected by immunohistochemistry in the tumor tissues. The percentage of CD4+CD25+CD127low/- Treg among CD4+ T cells was significantly higher in PTC patients than that in multinodular goiter (MNG) patients. There were large numbers of tumor-infiltrating FoxP3+ Treg in primary PTC and metastatic lymph nodes tissues; however, there was no FoxP3 expression in the MNG tissues. Higher percentage of Treg both in peripheral blood and tumor tissues was associated with extrathyroidal extension and lymph nodes metastasis. The percentage of CD4+CD25+CD127low/- Treg among CD4+ T cells in peripheral blood of PTC patients with Hashimoto's thyroiditis (HT) was significantly lower, whereas the infiltration of FoxP3+ Treg in tissues of PTC with HT tended to be increased. We concluded that the percentage of Treg increased in peripheral blood as well as in the tumor tissues of PTC patients compared with that of MNG patients. The high percentage of Treg was associated with aggressiveness. There may be a compensatory expansion of Treg at the sites of inflammation in tissues of PTC with HT contributing to the immune response suppression.