T cell receptor repertoire in polymyositis: Clonal expansion of autoaggressive CD8+ T cells

Abstract

In polymyositis (PM), CD8+ T cell receptor (TCR) α/β+ cells invade and destroy major histocompatibility complex class I-positive muscle fibers. We combined polymerase chain reaction (PCR) and double-fluorescence immunocytochemistry to analyze the T cell receptor (TCR) repertoire expressed in muscle of PM patients. In patient 1, inverse PCR revealed a preferential usage of TCR Vα33.1, Vβ13.1, and Vβ5.1. Six of six TCR Vα33.1+ clones and five of seven Vβ13.1+ clones had identical nucleotide sequences. In contrast, the Vβ5.1+ TCRs were more heterogeneous. Similar results were obtained with an independent PCR method using primers specific for TCR Vα33, Vβ13, or Vβ5. No TCR sequences could be amplified from noninflammatory control muscle. Furthermore, none of the TCR sequences found in PM muscle could be detected in blood from the same patient or from a normal control subject. Immunohistochemistry confirmed that Vβ5.1 and Vβ13.1 were overrepresented in the muscle lesions of this patient. 32% of all CD8+ T cells were Vβ13.1+, and 16% were Vβ5.1+. However, ~60% of the CD8+ T cells that invaded muscle fibers were Vβ13.1+, whereas 10% were Vβ5.1+. In patient 2, 50% of the T cells were Vβ5.1+, and as in patient 1, these T cells were mainly located in interstitial areas. In patient 3, >75% of the autoinvasive T cells stained with an anti-Vβ3 mAb. Sequence analysis of 15 PCR clones amplified with a Vβ3-specific primer showed that 9 (60%) sequences were identical. The results suggest that (a) a strikingly limited TCR repertoire is expressed in PM muscle; (b) there is a dissociation between the TCR usage of autoinvasive and interstitial T cells; and (c) the autoinvasive T cells are clonally expanded.