Complement factor H-related protein 3 is a protein that in humans is encoded by the CFHR3 gene. It is a secreted protein that belongs to the complement factor H protein family. Members of the H-related protein family are exclusively composed of individually folded protein domains. CFHR3 is synthesized as a 330 amino acid precursor that contains an 18 amino acid signal peptide and a 312 amino acid mature chain. Human CFCR3 protein might be involved in complement regulation.

Factor H is the major soluble inhibitor of complement, where its binding to self markers (i.e., particular glycan structures) prevents complement activation and amplification on host surfaces. Not surprisingly, mutations and polymorphisms that affect recognition of self by factor H are associated with diseases of complement dysregulation, such as age-related macular degeneration and atypical haemolytic uremic syndrome. In addition, pathogens (i.e., non-self) and cancer cells (i.e., altered-self) can hijack factor H to evade the immune response.

CFHR2 belongs to the complement factor H protein family. The human complement factor H protein family consists of the complement and immune regulators factor H, the factor H-like protein 1(FHL-1) and five factor H-related proteins (CFHR-1 to -5). Members of the H-related protein family are exclusively composed of individually folded protein domains, termed short consensus repeats (SCRs) or complement control modules. CFHR2 contains 4 Sushi (CCP/SCR) domains and is expressed by the liver and secreted in plasma. CFHR2 might be involved in complement regulation. It can associate with lipoproteins and may play a role in lipid metabolism.