Final answer:
CD59, or protectin, is crucial in protecting human cells by inhibiting the formation of the membrane attack complex (MAC) on human cell surfaces to prevent cellular damage by the immune system.
Step-by-step explanation:
CD59, also known as protectin, serves an important function in the protection of human cells against the formation of a membrane attack complex (MAC). MAC is part of the body’s immune defense and can kill pathogens by disrupting their osmotic balance. However, to protect human cells from being damaged by this defensive mechanism, CD59 inhibits the MAC formation on human cell surfaces. Therefore, regarding the quiz question, CD59 inhibits MAC formation.