Involved in complement regulation. The dimerized forms have avidity for tissue-bound complement fragments and efficiently compete with the physiological complement inhibitor CFH. Can associate with lipoproteins and may play a role in lipid metabolism. Head-to-tail homodimer and heterodimer with CFHR2 or CFHR5. (Microbial infection) Interacts with C.albicans GPD2; the interaction is direct and leads to the degradation of C3. Expressed by the liver and secreted in plasma. N-glycosylated. Two forms are observed; one with a single side chain and the other with two. Disease susceptibility is associated with variants affecting the gene represented in this entry. A deletion encompassing CFHR1 and CFHR3 is associated with an increased risk of atypical hemolytic uremic syndrome, likely due to a defective regulation of complement activation (PubMed:17367211). Some patients carrying the deletion have serum anti-CFH autoantibodies (PubMed:18006700).