Figure S4.

The length of protein-free DNA does not impact binding of anti-dsDNA IgG from SLE patients. (A) The effect of DNA length on binding to anti-dsDNA Abs as measured in a competition assay. Plasma from SLE patients was incubated with increasing concentrations of PCR-amplified DNA products of different lengths (95 bp, 186 bp, 382 bp, and 831 bp), and the binding of IgG to calf thymus dsDNA was assessed by ELISA. Dashed line shows binding in the absence of competitor DNA. Shown is a representative example of the data quantified for five plasma samples (also used in Fig. 5 F). (B) The effect of DNA length on binding to anti-dsDNA Abs as measured by ELISA. Plate-bound PCR-amplified DNA products of different lengths (95 bp, 186 bp, 382 bp, and 831 bp) were used as Ag to assess anti-dsDNA Abs from plasma of SLE patients. Calf thymus dsDNA, used in standard anti-dsDNA measurements, was used as a control. Shown is a representative example of five patients tested. In both approaches, data are representative of two independent experiments.