Proliferative Responses of Peripheral Blood Mononuclear Cells from Patients with Graves' Disease to Synthetic Peptides Epitopes of Human Thyrotropin Receptor

In Graves' disease thyrotropin receptor (TSH-R) autoantibodies cause hyperthyroidism. Production of TSH-R autoantibodies must be controlled by specific T cells. In this study we investigated T cell responses to 33 peptides corresponding to the sequence of the extracellular domain of human TSH-R. Peripheral blood mononuclear cells (PBMC) from 12 patients with Graves' disease and 9 healthy subjects were cultured with peptides for 3 days. The proliferative responses of PBMC were analyzed by measurement of [³H]thymidine incorporation. A stimulation index (SI; mean cpm in the presence of peptide/mean cpm in culture medium alone) of more than 3 was considered a positive response. When PBMC were stimulated with a pool containing all synthesized peptides, the mean SI of patients was significantly higher than that of controls (4.50 ± 3.95 vs. 1.44 ± 0.60; p < 0.05). When PBMC were cultured with individual peptides, PBMC from patients responded predominantly to two peptides, corresponding to sequence segments 152–157 (5 patients) and 207–222 (4 patients). No PBMC from controls responded to these two peptides. There was no clear correlation between the HLA-DR or HLA-DQ genotype and the stimulatory sequence segments. These results suggest that (a) TSH-R-specific T cells are present in peripheral blood of patients with Graves' disease, and (b) sequence segments 152–157 and 207–222 may be T cell epitopes of the human TSH-R in Graves' disease.