Analysis of serum binding to DNA and other ligands in systemic lupus erythematosus.

Using a solid-phase immunoassay (ELISA), serum binding to dsDNA, cardiolipin, beta 2-microglobulin (beta 2m) and Keyhole limpet haemocyanin (KLH) has been investigated in patients with systemic lupus erythematosus (SLE). Serum binding to DNA, cardiolipin and beta 2m was significantly increased in SLE sera, compared with normal sera; in addition, serum binding to KLH was also significantly increased. There were, however, no significant correlations between serum binding indices to DNA, beta 2m, cardiolipin or KLH; furthermore, in inhibition experiments no clear cross-reactions of lupus sera for these four ligands were detected. These data indicate that SLE sera bind to DNA, as well as to other apparently diverse ligands. Increased serum binding to these ligands may be attributable to a particular characteristic of the immunoglobulin molecules--or groups of immunoglobulin molecules - produced in these patients.