Using peripheral blood immune signatures to stratify patients with adult and juvenile inflammatory myopathies

The inflammatory idiopathic myopathies (IIM) are a group of rare autoimmune diseases defined by muscle weakness and characterized by pro-inflammatory infiltrates in muscle. Little is known about the immunological profile in peripheral blood of these patients and how this relates to IIM subtypes. This study aimed to stratify adult and juvenile-onset IIM patients according to immune cell profile.

Peripheral blood mononuclear cells from 44 patients with adult myositis (AM), 15 adolescent-onset juvenile dermatomyositis (a-JDM), and 40 age-matched healthy controls were analysed by flow cytometry to quantify 33 immune cell subsets. Adult myositis patients were grouped according to myositis subtype; DM and polymyositis; and also autoantibody specificity. Disease activity was determined by the myositis disease activity assessment tool and clinicians' decision on treatment.

Unique immune signatures were identified for DM, polymyositis and a-JDM compared with healthy controls. DM patients had a T-cell signature comprising increased CD4+ and TH17 cell frequencies and increased immune cell expression of IL-6. Polymyositis patients had a B-cell signature with reduced memory B cells. A-JDM had decreased naïve B cells and increased CD4+T cells. All patient groups had decreased CD8+central memory T-cell frequencies. The distinct immune signatures were also seen when adult myositis patients were stratified according to auto-antibody expression; patients with anti-synthetase-antibodies had reduced memory B cells and patients with autoimmune rheumatic disease overlap had an elevated Th17 profile.

Unique immune signatures were associated with adult vs juvenile disease. The Th17 signature in DM patients supports the potential use of IL-17 inhibitors in treatment of IIMs.