Characterization of mononuclear exudates in idiopathic inflammatory myopathies.

Percentages of B-cells, T-cells and subsets Th, Ts, T activated, and macrophages were analyzed by using monoclonal antibodies in a series of 24 patients [19 dermatomyosis (DM) and 5 polymyositis (PM)]. Specific site of deposition of these cells was also identified (endomysial, perimysial and perivascular). We were able to find a greater number of endomysial T-cells in PM than in DM. However, B-cells were more frequent at perivascular sites in DM than in PM. These findings support the previous reported hypothesis that humorally-mediated immune damage in both vascular and muscle cells predominates in DM while cellular cytotoxic mediated damage is more marked in PM patients.