Figure 1.

Dependence of C4 deposition assay on C4 serum concentration. C4 deposition was measured in a dilution curve of serum of two healthy donors in the presence of a constant mannose-binding lectin concentration of 200 ng/ml. C4 deposition becomes C4-dependent at a concentration below 0.001 g/l. Because sera with low C4 deposition (<10%) are evaluated at a dilution of 1:10, the minimal required C4 concentration in a tested serum will be 0.01 g/l.