Complement protein C5 is a crucial component of the immune system, part of the complement system that helps the body fight infections. It plays a key role in the inflammatory response by being cleaved into two fragments, C5a and C5b. C5a acts as a powerful chemotactic factor, attracting immune cells to sites of infection, while C5b initiates the formation of the membrane attack complex. The activation of C5 is essential for the opsonization of pathogens, enhancing their recognition and destruction by phagocytes. Dysregulation of C5 can lead to various diseases, including autoimmune disorders and chronic inflammation, highlighting its importance in maintaining immune balance.