Role of regulatory T cells in pathogenesis and therapeutics of dermatomyositis and polymyositis

Idiopathic inflammatory myopathies are a group of rare diseases characterized by systemic inflammation and autoimmune responses involving muscle tissue, skin, lungs, and other organs. The major subtypes are polymyositis (PM) and dermatomyositis (DM). However, clinical features and detection of specific autoantibodies could help to identify subgroups and associated syndromes like antisynthetase. Regulatory T cells (Tregs) are a subpopulation of T lymphocytes, which seems to have the role of limiting the immune response and maintaining homeostasis. In autoimmune diseases, Tregs are able to reduce the production of proinflammatory cytokines and T lymphocyte activity, so among the mechanisms underlying the development of autoimmunity, a deficit of their function or production may coexist. In this chapter, we discuss the role of Tregs in myositis, in particular PM and DM, focusing on their involvement in pathogenesis and the effect of conventional treatments on Tregs activity. Moreover, we mention therapies in clinical trials that act on Tregs and could be useful in disease management.