Figure 2. OmCI inhibits the ability of human and quail complement to initiate antibody-mediated erythrocyte lysis.

Sheep erythrocytes previously treated with anti-erythrocyte antibody were incubated with indicated concentrations of OmCI as well as human or quail serum with a final concentration as 5 % or PBS buffer (control) for 1 h. The levels of erythrocyte lysis were evaluated by measuring the absorbance at 405 nm of the supernatant from the reactions. The absorbance values at 405 nm of each reaction were normalized to that obtained from incubating these erythrocytes with water in the absence of OmCI. The work was performed on three independent experiments; within each experiment, samples were run in triplicate. The result shown here is the experiment (A) 1, (B) 2, and (C) 3 from the average percent lysis ± standard deviation of three replicates in each experiment. The concentration of OmCI to inhibit 50 % of erythrocyte lysis (IC₅₀) in the presence of human (blue) and quail (red) serum was obtained by fitting the data points using nonlinear regression methods (IC₅₀ = 6.80 ± 1.07 nM for human serum, IC₅₀ = 7.15 ± 0.61 nM for quail serum).