Altered cytokine expression of peripheral blood lymphocytes in polymyositis and dermatomyositis

Objective: To investigate the intracellular and soluble cytokine levels and T cell subsets in peripheral blood of patients with active and inactive polymyositis and dermatomyositis. Methods: The frequencies of T and B lymphocytes, T helper (Th), and T cytotoxic (Tc) cells and of interferon gamma (IFN gamma), interleukin ( IL) 4, and IL10 expression of CD4+ or CD8+ cells were determined by flow cytometry. The concentrations of soluble cytokines were measured with commercial enzyme linked immunosorbent assays. Results: In active dermatomyositis there was a decreased percentage of T (CD3+) lymphocytes and Tc (CD8+) lymphocytes, decreased IFN gamma expression of CD4+ and CD8+ cells, but an increase in B and IL4 producing CD4+ lymphocyte frequencies. These prominent changes disappeared in the inactive stage of the disease. In polymyositis no significant change in these lymphocyte subsets or in intracellular cytokine expression could be detected in either the active or the inactive form. The frequency of IL4+/IFN gamma+ Th cells was calculated and a significantly increased Th2/Th1 frequency was found in active dermatomyositis, and a decreased frequency in inactive dermatomyositis, compared with the control population. Conclusions: There appears to be a difference between polymyositis and dermatomyositis in the level of peripheral blood lymphocytes and their intracellular cytokine content. These findings provide further evidence for a difference in the pathogenesis of polymyositis and dermatomyositis.