Description
Complement factor H (CFH) is the first regulatory protein of the alternative pathway of the complement system. There are three ways to activate complement. The classical pathway is triggered by immune complexes. Surface-bound mannan-bound lectin pathways; and all surfaces that are not specifically protected. Each produces C3 convertase, a serine protease that cleaves the central complement protein C3 and produces the main cleavage fragment C3b. The complement system mediates many basic biological functions and participates in the host's resistance to infection, the initiation of inflammatory responses, the processing and clearance of immune complexes, and the regulation of immune responses. CFH is a 150 kD single-chain serum glycoprotein with a modular structure consisting of 20 homologous units of about 60 amino acids in series, called short consensus repeat (SCR). Many functional sites have been identified along the 20 SCR domain structure of Factor H. In SCR6-10 and SCR13-20 in SCR1-4. Three polyanionic binding sites have also been identified in SCR7, 13 and 20, such as heparin and several glycosaminoglycans. FH shows anti-inflammatory function and acts as a ligand for CRP. CFH has two important functional domains located at opposite ends of the protein. The N-terminal fragment of the factor H molecule is an essential liquid phase regulator for the alternative pathway. CFH binds to the surface of cells and tissues through the C-terminal domain and SCR 7, thereby mediating its protective effect on the surface of host cells. CFH is a relatively abundant plasma protein with a concentration of 400-800µg/ml, which is essential for maintaining the homeostasis of complement and limiting the effect of complement on activated surfaces. CFH binds to C3b, accelerates the decay of bypass C3 convertase (C3bBb), and acts as a cofactor for factor I-mediated C3b proteolytic inactivation. Factor H regulates complement on the liquid phase and on the cell surface. Genetic analysis shows that there is a clear association between CFH and different human diseases. These diseases include the kidneys, atypical forms of hemolytic uremic syndrome (aHUS) and membranous proliferative glomerulonephritis (MPGN), and age-related macular degeneration (AMD)