C3 and age-related macular degeneration: Several genes encoding proteins involved in the complement pathway have been shown to be associated with susceptibility to AMD, including the complement factor H gene (CFH) on chromosome 1q32 [3]–[5], two neighboring genes, complement component 2 (C2) and complement factor B (CFB) on 6p21 [6]–[8], the complement factor I gene (CFI) on 4q25 [9], [10], and the complement component 3 gene (C3) on 19p13 [11]–[13].