title: Quantitative aspects of lupus anti-DNA autoantibody specificity.
abstract: In this study we have attempted to define the cross-reactive potential of SLE anti-DNA antibodies (in 19 representative sera and plasmas) in both the solution phase and the solid phase. We used the Farr and RBC-CF solution phase assays to measure quantitatively the ability of a variety of negatively charged structurally unrelated molecules to inhibit antibody binding to both native DNA (nDNA) and denatured DNA (dDNA). The inhibitors used were of two types: 1) phospholipids (cardiolipin, phosphatidyl glycerol, and phosphatidic acid) and 2) repeating negatively charged molecules (poly-glutamic acid, heparin sulfate, and chondroitin sulfate). We found in both assays that the phospholipids could inhibit antibody binding to nDNA and dDNA, but a large excess (about 1500-fold) of these molecules was needed relative to DNA to achieve equivalent levels of inhibition. The repeating negatively charged molecules did not inhibit DNA binding at equivalent molar levels as the phospholipids; generally, at least a 10,000-fold excess was needed relative to the nucleic acids to achieve any appreciable inhibition. Results of a dDNA binding-inhibition solid-phase ELISA for cross-reactivity of the anti-DNA antibodies gave quite similar results. Finally, we found that eight of the SLE samples did have anti-cardiolipin antibodies, as demonstrated in a cardiolipin-based ELISA. These results suggest that previous reports describing an apparent cross-reactivity of anti-DNA antibodies may not represent physiologically relevant interactions between anti-DNA antibodies and non-nucleic acid antigens.
mesh_terms: D000974:Antibodies, Antinuclear / Q000032:analysis*; D000918:Antibody Specificity / Q000187:drug effects; D001666:Binding Sites, Antibody / Q000187:drug effects; D001667:Binding, Competitive; D002138:Calibration; D003168:Complement Fixation Tests / Q000592:standards; D004247:DNA / Q000276:immunology* / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D010743:Phospholipids / Q000494:pharmacology; D011108:Polymers / Q000494:pharmacology; D011869:Radioligand Assay / Q000592:standards
chemical_list: D000974:Antibodies, Antinuclear; D010743:Phospholipids; D011108:Polymers; D004247:DNA