Analysis of T cell receptor repertoire of muscle-infiltrating T lymphocytes in polymyositis. Restricted Vα/β rearrangements may indicate antigen-driven selection

Polymyositis is an inflammatory myopathy characterized by mononuclear cell infiltration of muscle tissue. Myocytotoxic T lymphocytes have been recognized in the infiltrates, but the muscle antigen, target of the immune attack, has not been identified. Molecular characterization of the variable regions of T cell receptors (TCRs) on the infiltrating lymphocytes can be expected to provide insights into the pathogenic process. The Vα/β TCR repertoire was investigated by RNA-PCR in muscle biopsies from 15 polymyositis patients and 16 controls (6 Duchenne muscular dystrophy and 10 with no inflammatory or dystrophic myopathy). A variety of rearranged variable TCR genes was found in polymyositis, Vα1, Vα5, Vβ1, and Vβ15 being the most common (present in 60-100% of patients). In Duchenne muscular dystrophy patients TCR Vα or β rearrangements were found although no restriction was observed; no rearrangements were found in muscles from the other controls. Sequence analysis revealed the presence of the Jβ2.1 region in 90% of the Vβ15 clones studied, no random N additions in the diversity region, and a common motif within the CDR3 region. These results suggest that selection of muscle-infiltrating T lymphocytes is antigen driven in polymyositis.