Neurology(R) Neuroimmunology & Neuroinflammation · Apr 10, 2019

PD1 pathway in immune-mediated myopathies: Pathogenesis of dysfunctional T cells revisited

By Knauss S, Preusse C, Allenbach Y et al.

OBJECTIVE: To investigate the relevance of dysfunctional T cells in immune-mediated myopathies. We analyzed T-cell exhaustion and senescence, in the context of programmed cell death protein 1 (PD1)-related immunity in skeletal muscle biopsies from patients with immune-mediated necrotizing myopathy (IMNM), sporadic inclusion body myositis (sIBM), and myositis induced by immune checkpoint inhibitors (irMyositis). METHODS: Skeletal muscle biopsies from 12 patients with IMNM, 7 patients with sIBM, and 8 patients with irMyositis were analyzed by immunostaining and immunofluorescence as well as by quantitative PCR. Eight biopsies from nondisease participants served as controls. RESULTS: CD3⁺CD8⁺ T cells in biopsies from IMNM, sIBM, and irMyositis were largely PD1-positive, while CD68⁺ macrophages were sparsely positive to the ligand of programmed cell death protein 1 (PD-L1). The sarcolemma of myofibers was PD-L2⁺ and was colocalized with major histocompatibility complex (MHC) class I. CD68⁺ macrophages were colocalized with PD-L2. Senescent T cells were strongly enriched in skeletal muscle of sIBM, revealing a distinct immunologic signature. Biopsies from patients with irMyositis showed mild signs of senescence and exhaustion. CONCLUSION: Persistent exposure to antigens in IMNMs and sIBM may lead to T-cell exhaustion, a process controlled by the PD1 receptor and its cognate ligands PD-L1/PD-L2. To our knowledge, these data are the first evidence of presence of dysfunctional T cells and relevance of the PD1 pathway in IMNM, sIBM, and irMyositis. These findings may guide the way to a novel understanding of the immune pathogenesis of immune-mediated myopathies.

doi.org/10.1212/nxi.0000000000000558Open accessPubMed 31044146Mechanisms