Fig. 1.

Binding of properdin to immobilized MPO. NHS in serial dilutions (A) or purified properdin diluted in VBS buffer (B) was incubated in microtiter plates coated with human neutrophil MPO dissolved in 0.05 M Na₂CO₃, pH 9.5, by overnight incubation at room temperature, or incubated solely with 0.05 M Na₂CO₃ as a control. All wells were subsequently blocked with 1.0% BSA in PBS (pH 7.4) and Tween (0.1%) for 60 min. NHS, serially diluted in 2.5 mM VBS, pH 7.2, with MgEGTA or purified properdin (2 μg/mL in VBS/MgEGTA), was incubated on MPO-coated surfaces or controls for 60 min at 37 °C. Binding of properdin was demonstrated in ELISA with mouse anti-human properdin. Data are presented as mean with 95% CI OD values for six experiments. ***P < 0.001.