Accumulation of Identical T Cell Clones in the Right and Left Lobes of the Thyroid Gland in Patients with Graves' Disease: Analysis of T Cell Clonotype in vivo

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To elucidate the involvement of intrathyroidal T cells in the thyroid antigen-specific immune response in Graves' disease (GD), we investigated whether identical T cell clonotypes accumulate clonally in the right and left lobes of thyroid glands of GD patients. mRNAs extracted from thyroid glands of five females patients with GD were reverse-transcribed to cDNA and then the genes coding the T cell receptor B chain variable (V-NDN-J) region were amplified using polymerase chain reaction. Single strand conformation polymorphism analysis and subsequently nucleotide sequencing were also performed to determine the clonotype of accumulating T cells. T cells infiltrating the thyroid glands showed oligoclonal expansion. The expanded T cell clonotypes were not detected in peripheral blood of the same patients. Importantly, the majority of expanding T cell clonotypes in the two lobes of the thyroid glands were identical. Our findings suggest that the clonal expansion of identical T cell clonotypes in the two lobes is driven by factors common to both lobes, such as thyroid-specific antigens, in patients with Graves' disease.