MLPA, Western blotting, and hemolytic assay. (A) MLPA results. The arrows indicate the position of the MLPA probes. Red arrows showed a probe ratio of 0.3 to 0.7. (B) Western blotting. Sera from a control person and one affected person from family A (IV:5) and purified fH (Comptech) were separated on 10% SDS-PAGE and transferred to nitrocellulose. fH was detected as described in “Western blotting.” A higher molecular weight band (indicated by the arrow) is seen in IV:5. (C) Hemolytic assay. Serum from an affected aHUS patient known to carry a heterozygous CFH/CFHR1 hybrid gene lyses the sheep red blood cells in a dose-dependent manner. Serum from an affected person (IV:5) known to carry the CFH/CFHR3 hybrid gene also lyses the cells but to a lesser extent. Sera from 2 unaffected persons (III:2 and IV:6) who carry the CFH/CFHR3 hybrid gene does not lyse the cells.