C3 and age-related macular degeneration: In addition, there are 5 FHR proteins (FHR1-5) that inhibit the actions of FH and FHL-1, thereby impeding C3b breakdown and driving complement activation; variations in and around genes encoding the FHR proteins, including CFHR1, CFHR2, CFHR4, and CFHR5, have been shown to be associated with, and indeed causal in, AMD.10, 11, 12, 13, 14