Objective To assess the prevalence of anti-alpha-enolase antibody in systemic autoimmune diseases in Chinese patients and its role in endothelial cell apoptosis.  Methods The reactivity of anti-alpha-enolase antibody in a variety of autoimmune disorders in Chinese patients was evaluated by dot blot assay. Endothelial cell apoptosis was investigated by in vitro incubation of endothelial cells with IgG purified from anti-alpha-enolase antibody-positive sera

with or without pre-incubation with recombinant alpha-enolase.  Results Anti-alpha-enolase antibody was prevalent in different systemic autoimmune diseases with relatively high reactivity in Chinese patients. In vitro incubation of endothelial cells with IgG containing anti-alpha-enolase antibody induced apoptosis in a time- and dose-dependent manner. Apoptosis was partly inhibited by pre-incubation of the endothelial cells with recombinant alpha-enolase.  Conclusions Our data suggest that alpha-enolase is a common auto-antigen recognized by anti- endothelial cell antibodies in connective tissue disease. Interaction between alpha-enolase and its autoantibody plays a role in endothelial cell apoptosis. Changes other than cell killing may contribute to the pathogenesis of endothelial damage and microvascular lesions.