Interaction between anti-DNA and anti-DNA-binding protein autoantibodies in cryoglobulins from sera of patients with systemic lupus erythematosus.

Abstract

We have previously shown that sera from some patients with SLE and related disorders contain autoantibodies to a DNA-binding protein complex designated p70/p80. The present study shows that anti-p70/p80 autoantibodies are frequently accompanied by anti-DNA antibodies and cryoglobulins. When the cryoglobulins were isolated, they were found to be specifically enriched in both anti-p70/p80 and anti-DNA activities. The anti-p70/p80 and anti-DNA antibodies were found to be distinct populations of autoantibodies rather than a single crossreactive species, since they could be separated from one another by chromatography on DNA-cellulose. Certain human anti-DNA mAbs could inhibit the binding of autoimmune polyclonal anti-p70/p80 antibodies to p70/p80, suggesting that anti-DNA antibodies might also associate with the variable regions of some anti-p70/p80 antibodies in the cryoglobulins. Binding of one murine anti-p70/p80 mAb (111-12) also was inhibited by certain human anti-DNA mAbs, but the binding of another murine mAb (162-11) to a different epitope of p70/p80 was not. These studies suggest that certain anti-DNA antibodies may interact with the variable regions of a population of anti-p70/p80 antibodies. The cryoglobulins found in the sera containing both anti-p70/p80 and anti-DNA antibodies may represent immune complexes consisting, in part, of idiotype and antiidiotype.