Recently, Sugihara et al. have established a murine model of polymyositis, which is called C protein-induced myositis (CIM) [10], and have shown that mice with CIM show pathological features similar to human polymyositis, including a massive infiltration of CD8+ T cells and macrophages in the endomysium of skeletal muscle [10]. The gene discussed is CD8A; the disease is polymyositis.