Persistent T cells identified in the muscle of patients with idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIM) are rare autoimmune diseases characterized not only by skeletal muscle weakness but also by a large variety of extra-muscular organ involvement, where treatment represents a challenge due to the variable response rate, often with disappointing results. The presence of T cell infiltrates in skeletal muscle is a hallmark of many subsets of IIM. However, a deeper analysis of T cells at the site of inflammation was still lacking and could help defining or predicting a better treatment for each patient as well as understanding the molecular pathophysiology.

We took advantage of the collection of muscle biopsies for diagnosis purposes to also perform a deeper analysis of T cells in muscle and blood of patients with IIM, says Karine Chemin, Karolinska Institutet, Department of medicine, Solna, Divison of Rheumatology. And continues:

The most important finding of this study is that we identify T cells which have features of tissue residency. We show that these cells are maintained within the muscle tissue despite immunosuppressive treatment. We postulate that these cells, which are expanded in the tissue, might contribute to relapses and disease chronicity. We also provide a deep transcriptomic analysis of these T cells, a molecular mapping, that we hope can be used to better understand the disease pathogenesis and to develop new therapeutic targets for difficult to treat patients.

The authors now aim to collect samples from more patients to have a better overview of the molecular differences between the different IIM subtypes.