Complement Factor H-Related 1 (CFHR1) is a 43 kDa secreted member of the factor H family of glycoproteins. 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. FHR1 is produced by hepatocytes and circulates as two differentially glycosylated isoforms (37 kDa and 43 kDa). Mature human FHR1 is 312 amino acids in length. It contains five, approximately 60 aa SCRs that basically constitute the entire molecule. FHR1 may play a role in complement regulation, lipid metabolism and lipoprotein complexes that bind PMNs to LPS.