CD4 and polymyositis: IIMs are characterized by high levels of circulating cytokines and chemokines, as well as by inflammatory cellular infiltrates, including macrophages, DCs, CD8+ T cells (predominantly affecting the endomysium in polymyositis) and CD4+ T cells, which affect the perimysium in dermatomyositis (Wiendl et al., 2005; Huang et al., 2018).