How is the pathogenesis of myositis?

Adaptive immunity (T cells, B cells, autoantibodies and D c) T cells (PM high proportion of CD8 T cells then CD4 T cells in endomysial infiltrates, DM more CD4 and macrophages in perivascular localisation in perimysium, CD28 null T cells can persist in muscles for a long time and resist immunosupressive therapy, Th17) B cells are less commonly found in infiltrates and more often perivascular localization in DM infiltrate, autoantibodies produced, pathogenic role increase with pathology, make antibody dependent cellular cytotoxicity and complement fixation