Anticardiolipin antibodies and disease activity in systemic lupus erythematosus

We studied a group of 80 unselected patients with systemic lupus erythematosus (SLE). Twenty six (32.5%) of them were considered in clinical activity using criteria based on clinical features and laboratory abnormalities. Using an isotype specific enzyme linked immunosorbent assay (ELISA) for anticardiolipin antibodies we found IgG anticardiolipin in 28/80 (35%) and IgM anticardiolipin in 20/80 (25%) patients. Antibodies to native DNA by immunofluorescence were found in 11/80 (14%) patients, whereas antibodies to denatured DNA by ELISA were found in 51/80 (64%) patients. There was an association between disease activity and the presence of anticardiolipin and anti-DNA antibodies particularly of the IgG isotype. We also found an association between anticardiolipin and anti-DNA suggesting a cross reaction between these antibodies, but we are not able to exclude the possibility of a simple coincidental phenomenon due to polyclonal synthesis of immunoglobulin observed during periods of disease activity.