Figure 2.

Validation of C9 direct ELISA. His-C9 was expressed and purified for use as the standard, and serum purified C9 was spiked into C9-depleted serum at three concentrations (20 µg/mL, 40 µg/mL and 80 µg/mL). (a) Concentration estimated by the ELISA was plotted against the spiked concentration. Dilutions of 1/1250 predicted the theoretical concentration accurately while higher dilutions underestimated the theoretical concentration when samples were spiked at 40 µg/mL and 80 µg/mL (n = 3). (b) Parallelism was determined by log10 calculation of dilution vs. estimated concentration of the spiked sample, demonstrating proportionate estimates of concentration at differing dilutions (n = 3).