title: The use of polyethylene glycol precipitation to detect low-avidity anti-DNA antibodies in systemic lupus erythematosus.
abstract: With a recently introduced method for measurement of low-avidity anti-DNA, the polyethylene glycol (PEG) precipitation assay (Riley et al., 1979), high levels of DNA binding by normal human serum (NHS) were found when circular PM2-DNA was used as antigen. THe nature of this DNA binding was studied. The removal of low-density lipoproteins (LDL) from the serum, e.g., by Aerosil absorption, eliminated DNA binding by NHS. Purified LDL bound DNA to the same extent as NHS. Non-specific binding of NHS or LDL to DNA was prevented by adding dextran sulphate to the incubation mixture. Analysis on sucrose gradients showed that only large DNA-anti-DNA complexes were precipitated by 3.5% PEG. The PEG assay with dextran sulphate is a sensitive assay for low-avidity anti-DNA antibodies. It adds important information to results obtained with the Farr assay, which mainly detects antibodies of high avidity.
mesh_terms: D000974:Antibodies, Antinuclear / Q000302:isolation & purification*; D000936:Antigen-Antibody Complex; D004247:DNA / Q000276:immunology; D005260:Female; D006801:Humans; D007163:Immunosorbent Techniques; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D011092:Polyethylene Glycols
chemical_list: D000974:Antibodies, Antinuclear; D000936:Antigen-Antibody Complex; D011092:Polyethylene Glycols; D004247:DNA