IgG subclass distribution of anticardiolipin antibody in patients with systemic lupus erythematosus.

IgG subclass distributions of anticardiolipin (aCL), anti-ssDNA, and anti-dsDNA antibodies in sera of patients with systemic lupus erythematosus were determined by an enzyme linked immunoassay (ELISA) method, using mouse monoclonal antihuman IgG subclass antibodies. IgG aCL activity consisted mainly of the IgG1 subclass, and to some extent, the IgG3 subclass. Definite amounts of aCL activity were also detected in IgG2 in sera from 25% of the patients. Anti-ssDNA antibody activity was relatively equally distributed among IgG1, IgG2 and IgG3, but was poorly distributed in IgG4. In contrast, anti-dsDNA antibody activity consisted mainly of IgG1 and IgG3.