CD55

CD55, also known as decay-accelerating factor (DAF), is a protein that in humans is encoded by the CD55 gene. CD55 is a member of the complement system, which is part of the immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane.

Structure and Function

CD55 is a glycoprotein that is anchored to the cell membrane via a glycosylphosphatidylinositol (GPI) anchor. It is widely expressed on the surface of blood cells, epithelial cells, and endothelial cells. The primary function of CD55 is to regulate the complement system on the cell surface by accelerating the decay of C3/C5 convertases, thereby preventing the formation of the membrane attack complex (MAC) and protecting host cells from complement-mediated lysis.

Clinical Significance

Mutations or deficiencies in CD55 can lead to a condition known as paroxysmal nocturnal hemoglobinuria (PNH), a rare, acquired, life-threatening disease of the blood characterized by complement-mediated hemolysis. CD55 deficiency can also contribute to other autoimmune and inflammatory conditions due to unregulated complement activation.

CD55 is also exploited by certain pathogens, such as Enterovirus and Coxsackievirus, which use it as a receptor to gain entry into host cells.

Research and Therapeutic Implications

Research into CD55 has implications for the development of therapies aimed at modulating the complement system. Therapeutic strategies may include the use of recombinant CD55 or small molecules that mimic its activity to treat diseases characterized by excessive complement activation.

Also see

• Complement system
• Paroxysmal nocturnal hemoglobinuria
• Glycosylphosphatidylinositol
• Immune system