Quantifying Serum MPO-DNA Complexes in SLE

Serum MPO-DNA complex levels of SLE patients and HCs were measured as previously reported^{18 (link)}. In brief, high-binding 96-well microplates (Corning) were incubated overnight at 4 °C with a mouse anti-human MPO antibody (clone 4A4; Bio-Rad) diluted in coating buffer (Cell Death Detection ELISA kit; Roche). Following blocking with 1% bovine serum albumin (cat# A2153; Sigma) in phosphate-buffered saline (PBS), plates were incubated at room temperature with 10% human serum in blocking buffer, washed, and then 10 × anti-DNA-POD (Clone MCA-33, Cell Death Detection ELISA kit; Roche) in blocking buffer was added. After the incubation, TMB substrate (KPL) was added, and absorbance was measured at 450 nm after the addition of the stop reagent (Wako). Serum MPO-DNA complex “high” patients were defined as those whose optical density values were two standard deviations higher the mean of HCs.