Complement factor H, also known as factor H1 and CFH, is a sialic acid-containing glycoprotein that plays an integral role in the regulation of the complement-mediated immune system, which is involved in microbial defense, immune complex processing, and programmed cell death.CFH acts as a regulator of the alternative pathways of the complement system by ensuring that the associated immune response acts on foreign pathogens that are not host cells. CFH protects self-cells from complement activation, but not bacteria and viruses.Misregulation of CFH may adversely affect the ability to deal with foreign infections or to reduce host cell complement activity.Mutations in the factor H gene have been associated with a variety of serious diseases, including the rare kidney disorders hemolytic uremic syndrome (HUS) and membranoproliferative glomerulonephritis (MPGN), also known as dense matter deposition disease ( DDD), type II membranoproliferative glomerulonephritis or dense deposit disease, and the more common age-related macular degeneration (AMD).