Decay Accelerating Factor (DAF) in the complement system primarily serves to:

Decay Accelerating Factor (DAF) in the complement system primarily serves to:

• A. Prevents complement activation on self cells
• B. Enhances alternative pathway
• C. Cleaves C3 to C3a
• D. Promotes formation of C5a

Answer: (A)

Decay-accelerating factor protects host cells by limiting complement activation on self surfaces. It does this by promoting the rapid dissociation of the C3 convertases that form on cell membranes—the classical/lectin pathway convertase (C4b2a) and the alternative pathway convertase (C3bBb). By disassembling these convertases, DAF blocks the amplification loop, reducing production of inflammatory fragments like C3a and C5a and preventing assembly of the membrane attack complex on the body's own cells. It does not cleave C3 to C3a itself, nor does it promote the pathways; its role is regulation to avoid damage to host tissue.

Decay-accelerating factor protects host cells by limiting complement activation on self surfaces. It does this by promoting the rapid dissociation of the C3 convertases that form on cell membranes—the classical/lectin pathway convertase (C4b2a) and the alternative pathway convertase (C3bBb). By disassembling these convertases, DAF blocks the amplification loop, reducing production of inflammatory fragments like C3a and C5a and preventing assembly of the membrane attack complex on the body's own cells. It does not cleave C3 to C3a itself, nor does it promote the pathways; its role is regulation to avoid damage to host tissue.