Dissociation studies of DNA/anti-DNA complexes in relation to anti-DNA avidity.
Antibodies to dsDNA differ in their avidity towards the antigen. The electrostatic interaction between DNA and anti-DNA is sensitive to increases in pH and/or ionic strength and therefore, elution studies employing either of these permit discrimination between anti-dsDNA populations that differ in avidity. Another way to determine anti-dsDNA avidity is the calculation of Farr/PEG ratios. These are obtained by division of the amount of anti-DNA measured with the Farr assay (which does not detect low avidity anti-dsDNA) by the amount measured with the PEG assay (which does detect low avidity anti-dsDNA). With these separate approaches, we compared the sera of 17 SLE patients with nephritis with the sera of 17 patients with central nervous system (CNS) involvement. Farr/PEG ratios and sensitivity to high pH elution of anti-dsDNA in the sera of these patients both permitted discrimination between the two groups of patients. The anti-dsDNA of patients with nephritis was found to have a significantly higher avidity towards DNA than anti-dsDNA of patients with cerebral disease. We also observed a significant correlation between Farr/PEG ratios and the salt lability of anti-dsDNA.
Smeenk
R J
RJ
Central Laboratory, Netherlands Red Cross Blood Transfusion Service, Amsterdam.
Van Rooijen
A
A
Swaak
T J
TJ
D000974:Antibodies, Antinuclear / Q000032:analysis* / Q000302:isolation & purification; D000915:Antibody Affinity; D000936:Antigen-Antibody Complex / Q000378:metabolism*; D004247:DNA / Q000276:immunology*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007158:Immunologic Techniques; D008180:Lupus Erythematosus, Systemic / Q000276:immunology; D011092:Polyethylene Glycols
D000974:Antibodies, Antinuclear; D000936:Antigen-Antibody Complex; D011092:Polyethylene Glycols; D004247:DNA