INTRATHYROIDAL T-CELL ACCUMULATION IN GRAVES-DISEASE - DELINEATION OFMECHANISMS 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 hypert hyroid Graves' disease. Radiolabeled RT-PCRs were performed with 18 V alpha and 21 V beta oligonucleotides as forward primers and P-32-label ed constant(C) region oligonucleotides as reverse primers, giving 273 experiments in all. Peripheral blood mononuclear cells showed CDR3 ban ding 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), represent ing within V gene family restriction, seen in 38/153 (25%) PCR positiv e samples. The second was the presence of markedly enhanced bands repr esenting either clonal expansion or accumulation of T cells using the same V gene and with the same CDR3 length and observed in 15/153 (10%) of samples. Further examination of the enhanced bands by sequencing o f gel-selected PCR-amplified V gene products showed the presence of bo th T cell clonal expansion, as evidenced by similar CDR3 sequences, an d in a few samples, heterogenous T cell populations, as evidenced by d iffering CDR3 sequences, yet all sharing the same V gene family. These data support the hypothesis that the human intrathyroidal T cell popu lation in Graves' disease was selected by two distinct mechanisms. The first was associated with the TcR V gene invariant product and repres ented by nonclonal accumulation of T cells sharing the same V gene. Th e second mechanism responsible for T cell accumulation was specific an tigen recognition by the human T cell receptor CDR3 region and was rep resented by clonally expanding T cells.