The mAb 1C9 binds to both free C6 and C6 within C5b6 complexes. An ELISA plate was coated with 1 nM of purified C6, C5b6, or C5 and then incubated with different dilutions of 1C9 (maximum, 1 μg/mL). After washing and development, the binding of 1C9 in each well was measured by reading the optical density at 450 nm (OD450). Negative controls (Ctrl) were wells to which the highest concentration of mouse IgG (1 μg/mL) was added. Data represent mean ± standard deviation in triplicate wells. Representative results from 2 independent experiments.