Human Complement Decay-Accelerating Factor (CD55) Protein

Background

CD55, also known as decay-accelerating factor (DAF), is a glycoprotein that plays a critical role in regulating the complement system, a part of the innate immune response. The primary function of CD55 is to protect host cells from complement-mediated damage by inhibiting the formation of C3 and C5 convertases, key enzymes in the complement activation pathways. CD55 is widely expressed on the surface of many cell types, including erythrocytes, leukocytes, endothelial cells, and epithelial cells. Its expression is essential for preventing unintended complement activation on host tissues, which could lead to cell lysis and tissue damage. CD55 is particularly important in safeguarding cells from the alternative pathway and classical pathway of complement activation. The complement system is a major defense mechanism that helps the body clear pathogens through opsonization, inflammation, and lysis of infected or foreign cells. By regulating this system, CD55 ensures that the complement system does not damage self-cells, thus maintaining tissue integrity during immune responses.