Objective: Polymyositis (PM) and dermatomyositis (DM) are idiopathic inflammatory myopathies; autoimmune mechanisms are thought to play an important role in their pathogenesis. We investigated the immunocytochemical characteristics and Th1/Th2 balance of peripheral blood lymphocytes in PM and DM using flow cytometry.
Patients and methods: Eight patients with PM and 13 with DM were enrolled in this study. Of these, 8 patients with DM were examined before and after clinical remission. No patients were receiving any treatment for PM or DM at enrollment. Ten healthy subjects were used as controls.
Results: Patients with PM showed significant increases in CD3+CD4+HLA-DR+ (p<0.01) and CD19+CD23+ cells (p<0.05), and significant decreases in CD3+CD4+ (p<0.005) and CD4+CD45RO+ cells (p<0.05) compared with controls. Patients with DM showed significant increases in CD19+ (p<0.05) and CD19+CD23+ cells (p<0.05), and significant decreases in CD4+CD45RO+ cells (p<0.005) and the CD4+CD45RO+/CD4+CD45RA+ ratio (p<0.005) compared with controls. CD4+interferon (IFN)-gamma+ cells and the intracellular IFN-gamma/interleukin (IL)-4 ratio in CD4+ cells were significantly lower in patients with DM than in those with PM (p<0.05) or controls (p<0.0005 and p<0.001, respectively). The intracellular IFN-gamma/IL-4 ratio in CD4+ cells was significantly increased in DM after clinical remission compared with before (p<0.05).
Conclusion: Both B and helper T cells are activated in peripheral blood of active PM. Th2 cells predominate in peripheral blood of active DM, and the intracellular IFN-gamma/IL-4 ratio in CD4+ cells may be useful as a clinical marker indicating disease activity.