Question

Decay accelerating factor (DAF) on the surface of blood cells protects against complement-mediated damage by inhibiting C3 convertase specific. The RBC membrane also contains MIRL which has a similar protective effect by preventing C9 from polymerizing. What is the function of Decay accelerating factor (DAF) on the surface of blood cells?

1) Inhibiting C3 convertase specific
2) Preventing C9 from polymerizing
3) Protecting against complement-mediated damage
4) Promoting blood cell growth

Answer 1

Decay Accelerating Factor (DAF) protects blood cells from complement-mediated damage by inhibiting the C3 convertase enzyme, as opposed to MIRL, which prevents C9 polymerization to avoid the formation of the membrane attack complex. The correct option is 1) Inhibiting C3 convertase specific

Step-by-step explanation:

The function of the Decay Accelerating Factor (DAF) on the surface of blood cells is protecting against complement-mediated damage by inhibiting the C3 convertase. DAF disrupts the formation and function of C3 convertases, which cleave the complement component C3, initiating opsonization and inflammatory processes.

This action helps to protect the host's own cells from being targeted by the complement system, ensuring that only pathogens are marked for destruction.

In comparison, MIRL (CD59) works by preventing C9 from polymerizing and forming the membrane-attack complex - part of the final step in the complement activation sequence that can lyse pathogens and host cells alike when unchecked. The correct option is 1) Inhibiting C3 convertase specific