Interactions of anti-DNA antibodies with Z-DNA.

Systemic lupus erythematosus (SLE) sera, two classes of serum lipoproteins, and IgG antibodies from SLE and normal sera were tested for their reactivity with a Z-DNA polymer, Br-poly (dG-dC). In all cases preferential binding to Z-DNA over B-DNA was observed. This interaction, for the most part, could be inhibited by the negatively charged phospholipid, cardiolipin, which suggests that most of the anti-Z-DNA activity associated with sera arises from relatively non-specific ionic interactions between proteins and polyanionic molecules. An assay has been described that can eliminate proteins cross-reactive with negatively charged phospholipids.