Antinuclear Antibodies in Systemic Lupus Erythematosus

A new method for performing the antinuclear antibody test using antibody labeled with horseradish peroxidase is described. Rabbit antibody to human IgG was conjugated to horseradish peroxidase and used to demonstrate adherence of antinuclear antibodies to the nuclei of mouse liver. Localization of the enzyme was demonstrated by its reaction with 3,3′ diaminobenzidine, which gives an insoluble brown reaction product. Sera from patients with systemic lupus erythematosus and other connective tissue diseases were tested. Thirty-four of 36 patients with systemic lupus erythematosus, 8 of 25 patients with rheumatoid arthritis, and 6 of 11 patients with progressive systemic sclerosis had demonstrable antinuclear antibodies by the peroxidase technique as compared with none of 17 normal controls. These results correlated well with the standard test using antibody labeled with fluorescein isothiocyanate. Sera from patients with systemic lupus erythematosus generally had a higher titer of antinuclear antibody than sera from patients with rheumatoid arthritis or progressive systemic sclerosis. Patterns of nuclear staining were observed in the peroxidase technique and appeared to correlate with the patterns obtained by the fluorescent antibody method. Advantages of peroxidase-labeled antibody included reproducibility of the technique, ease of standardization, lack of nonspecific staining, and use of conventional light microscope.