CD4 and dermatomyositis: The types of immune cells present in myositis muscle were originally identified in the 1980s as predominantly CD4+ T cells and B cells in DM, and CD4+ and CD8+ T cells in IBM [1,6-8], with more recent identification of plasmacytoid dendritic cells in DM [9], myeloid dendritic cells in PM and IBM [3], and plasma cells in all three disorders [2].