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To investigate whether sera or purified IgG from patients with polymyositis (PM) and patients with dermatomyositis (DM), with or without interstitial lung disease (ILD), can activate endothelial cells (ECs).
Patients' sera were selected based on the presence or absence of anti–Jo-1, anti-SSA, or anti–U1 small nuclear RNP autoantibodies. The presence of autoantibodies was determined by line blot assays. Cultured human microvascular ECs derived from lung tissue (HMVEC-L) were incubated with sera or purified IgG from 22 patients with PM, 7 patients with DM, and 10 healthy individuals as controls. Assessment of intercellular adhesion molecule 1 (ICAM-1) expression was conducted by immunofluorescence (n = 22) and by cell-based enzyme-linked immunosorbent assay (ELISA) (n = 20). Serum levels of soluble ICAM-1 (sICAM-1) were determined by ELISA.
Sera from PM patients with ILD who were positive for anti–Jo-1 autoantibodies had a significantly stronger effect on the expression of ICAM-1 by HMVEC-L in comparison with sera from healthy controls and patients with other autoantibodies. Purified IgG did not induce ICAM-1 expression. Higher serum levels of sICAM-1 were found in patients with myositis compared with healthy controls.
EC activation with ICAM-1 expression could contribute to the multiorgan involvement, including the development of myositis and ILD, in patients carrying anti–Jo-1 autoantibodies. The EC-activating factors are not the autoantibodies themselves, but might be systemic factors associated with these autoantibodies.