The use of fluorometric assays to assess the immune response to DNA in murine systemic lupus erythematosus.
Antibodies to DNA (anti-DNA) play an important role in the pathogenesis of systemic lupus erythematosus (SLE). In blood, these antibodies may exist in a free, unbound state or as part of complexes with DNA. Furthermore, circulating DNA may be either complexed or free. Because of the central role of these immunoreactants (anti-DNA and DNA) in the disease, monitoring of their levels could provide valuable information for both clinical and investigative purposes. In these studies, we have explored the use of a DNA-binding dye, PicoGreen, for the detection of circulating DNA, either total or immune complex bound. In addition, we have used this dye for Farr-type antibody assays. Using autoimmune MRL/lpr mice as a model, we have shown that, while the levels of free DNA in the plasma of these mice were comparable with those of normal BALB/c mice, the amounts in complexes precipitable by ammonium sulfate were significantly greater. Furthermore, we showed that Farr assays using PicoGreen reliably detect levels of free anti-DNA, with values correlated with anti-DNA levels by an enzyme-linked immunosorbent assay. Together, our results suggest that a fluorometric dye can accurately monitor DNA and anti-DNA antibody levels in SLE and may provide important information on immunopathogenesis.
Björkman
L
L
Medical Research Service, Durham Veterans Administration Hospital and Division of Rheumatology, Duke University Medical Center, Durham, NC, USA.
Reich
C F
CF
Pisetsky
D S
DS
D000645:Ammonium Sulfate; D000818:Animals; D000974:Antibodies, Antinuclear / Q000097:blood*; D001774:Blood Chemical Analysis / Q000379:methods; D011232:Chemical Precipitation; D004247:DNA / Q000097:blood* / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique / Q000379:methods*; D005456:Fluorescent Dyes; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D019463:Mice, Inbred MRL lpr; D009930:Organic Chemicals
D000974:Antibodies, Antinuclear; D005456:Fluorescent Dyes; D009930:Organic Chemicals; C099476:PicoGreen; D004247:DNA; D000645:Ammonium Sulfate