Use of enzyme-linked antibodies to measure serum anti-DNA antibody in systemic lupus erythematosus.

We describe a solid-phase adsorbent enzyme-linked immunoassay for measuring the amount of antibody in serum. The assay consists of adsorbing an excess of DNA to a polystyrene test-tube support, reacting the anti-DNA serum with the coated tube, following with an additional reaction of an anti-human -y-globulin peroxidase enzyme conjugate with the coated tube, and finally developing a colored reaction product by the action of peroxidase on substrate. In principle, the amount of lgG bound to the tube is proportional to the amount of anti-DNA contained in the serum, and the conjugate also reacts proportionally to the amount of human lgG that has reacted. The assay gives data Consistent with that expected for serum from patients with systemic lupus erythematosus, and it is possible to titrate the serum for micrograms of DNA antibody. At present the method still has considerable variability, but offers a new approach to measurement of antibody in autoimmune diseases.