An ELISA procedure to detect anti-double-stranded and anti-single-stranded DNA binding antibodies in connective tissue disorders.

A simple and sensitive enzyme-linked immunosorbent assay (ELISA) is described for the measurement of antibodies to native DNA (double-stranded) and to heat-denatured DNA (single-stranded) in sera of patients with connective tissue disorders. DNA bound to polyvinylchloride plates is incubated with serum samples, and antibodies to both single- and double-stranded DNA are detected by means of goat antihuman IgG alkaline phosphatase conjugate. The binding in individual sera is expressed as binding units per milliliter and refers to the absorbance in relation to the absorbance value obtained with a set of standards. The various parameters of the ELISA assay are described, and the results are compared with results of the Crithidia and Farr DNA antibody assays. Two case reports are discussed.