Detection by Flow Cytometry of Anti-DNA Autoantibodies and Circulating DNA Immune Complexes in Lupus Erythematosus

Figure 2

Detection of immune complexes DNA-anti-DNA antibodies (IC-DNA). In the upper histograms, a serum sample of SLE incubated with 20 μg/ml ctDNA and in the lower histograms before incubation. SS is the side scatter; FL3 (620 nm) is fluorescence of DNA stained by EB and FL1 (525 nm) fluorescence due to antibody labeling by FITC-conjugated anti-human globulin. IC-eDNA, microparticles (MPs), and some free DNA already were present in the serum sample, but after incubation with ctDNA, the rate of IC-DNA increased significantly. The discriminator was EB fluorescence; only events stained by EB are shown. For each series of experiments, a gate was built around IC-DNA in order to quantify events. The parameters of this gate were defined by the SS, FITC fluorescence of the second antibody in FL1, and fluorescence of DNA stained by EB in FL3.