Studies on IgG-rheumatoid factor in systemic lupus erythematosus -Using the erythrocyte agglutination test-Part 2. Clinical studies

IgG-rheumatoid factor (IgG-RF) was detected in systemic lupus erythematosus (SLE) with a new method using sheep red blood cells sensitized with rabbit gammaglobulin, and antihuman IgG antibody. IgG-RF was positive in 15 of 50 SLE patients (30%) but the hemagglutination titer of IgG-RF was lower than 1:1024. The presence of IgG-RF did not correlate with any pattern of antinuclear factors, anti-DNA antibody titer, serum complement level, anticomplementary activity, erythrocyte sedimentation rate, gammaglobulin level or clinical symptoms. These findings suggest that IgG-RF may be a result of the immune reaction in SLE rather than a pathogenic factor.