Complement Factor H Related 4

Complement factor H-related protein 4 (CFHR4) is the largest FHR family member and occurs as two splice isoforms, CFHR4A and CFHR4B, which differ in domain composition. Unlike other FHR proteins, CFHR4A binds C1q, and CFHR4 has been found deposited on microbial surfaces and in the choroidal neovascular lesions of age-related macular degeneration, where it can locally enhance complement activation. The gene sits within the CFHR cluster at chromosome 1q32 whose copy-number variation shapes disease risk. Recombinant CFHR4 supports studies of isoform-specific binding, C1q interaction, and complement deregulation in ocular disease.