Intrathyroidal T cell accumulation in Graves' disease: delineation of mechanisms based on in situ T cell receptor analysis.

We have explored the pattern of T cell clonal and nonclonal expansion within the thyroid glands of 7 patients with surgically treated hyperthyroid Graves' disease. Radiolabeled RT-PCRs were performed with 18 V alpha and 21 V beta oligonucleotides as forward primers and 32 P-labeled constant (C) region oligonucleotides as reverse primers, giving 273 experiments in all. Peripheral blood mononuclear cells showed CDR3 banding patterns involving at least 6-12 distinct bands per V gene family. However, 2 distinct banding patterns were seen with intrathyroidal T cell samples. The first was a limited number of bands (< 6), representing within V gene family restriction, seen in 38/153 (25%) PCR positive samples. The second was the presence of markedly enhanced bands representing either clonal expansion or accumulation of T cells using the same V gene with the same CDR3 length and observed in 15/153 (10%) of samples. Further examination of the enhanced bands by sequencing of gel-selected PCR-amplified V gene products showed the presence of both T cell clonal expansion, as evidenced by similar CDR3 sequences, and in a few samples, heterogenous T cell populations, as evidenced by differing CDR3 sequences, yet all sharing the same V gene family. These data support the hypothesis that the human intrathyroidal T cell population in Graves' disease was selected by two distinct mechanisms. The first was associated with the TcR V gene invariant product and represented by nonclonal accumulation of T cells sharing the same V gene. The second mechanism responsible for T cell accumulation was specific antigen recognition by the human T cell receptor CDR3 region and was represented by clonally expanding T cells.