TCR Vβ Usage of TSH Receptor-specific CD4+T Cells in Graves' Disease Patients and Healthy Humans

Abstract

Healthy humans have CD4+T cells specific for self-components. Since autoreactive T cells in autoimmune patients may use a limited number of TCR V-region genes, we investigated here whether this also occurs for the potentially autoreactive CD4+cells present in healthy persons. We studied CD4+cells specific for human TSH receptor (TSHr) sequences, that are present with high frequency in healthy subjects and, as expected, in Graves’ disease (GD) patients.We used short-term CD4+cell lines propagated from four GD patients and five healthy subjects by cycles of stimulation with a pool of overlapping synthetic peptides corresponding to the putative extracellular parts of the TSHr sequence. The lines recognized the pool of TSHr peptides specifically and vigorously. Their epitope repertoire had been characterized previously: each line recognized one or a few TSHr peptides, different for each subject.We determined their TCR Vβ usage by a semi-quantitative reverse transcriptase PCR assay, using primers specific for each known human Vβ region family, in conjunction with a constant region primer. Six lines preferentially used one Vβ family (42–94%), different for each line. In all lines, three or less Vβ families accounted for approximately 60% or more of the Vβ usage. Different Vβ regions were used by each subject. There was no obvious difference between the Vβ usage of the lines from GD patients and healthy controls.These results suggest that a limited pool of potentially autoreactive T cells survives clonal deletion. The pathogenic CD4+cells involved in autoimmune diseases are likely recruited from that pool, since they have similar characteristics of epitope and TCR repertoire as the CD4+cells specific for the same autoantigen in healthy subjects.