What is the function of the C3 convertase in the complement cascade?

What is the function of the C3 convertase in the complement cascade?

• A. Cleaves C3 into C3a and C3b, enabling opsonization and formation of the MAC.
• B. Directly forms the membrane attack complex (MAC)
• C. Cleaves C5 into C5a and C5b
• D. Activates B cells via CD40

Answer: (A)

The function being tested is what C3 convertase does in the complement cascade. C3 convertase cleaves the central molecule C3 into C3a and C3b. C3b binds to the microbial surface, tagging it for phagocytosis (opsonization) and, together with other components, forms the C5 convertase that cleaves C5 into C5a and C5b. This cleavage cascade ultimately leads to the assembly of the membrane attack complex starting with C5b. So, C3 convertase’s key role is to generate C3b for opsonization and to drive the steps that produce MAC, not to directly form the MAC itself. It does not activate B cells via CD40.

The function being tested is what C3 convertase does in the complement cascade. C3 convertase cleaves the central molecule C3 into C3a and C3b. C3b binds to the microbial surface, tagging it for phagocytosis (opsonization) and, together with other components, forms the C5 convertase that cleaves C5 into C5a and C5b. This cleavage cascade ultimately leads to the assembly of the membrane attack complex starting with C5b. So, C3 convertase’s key role is to generate C3b for opsonization and to drive the steps that produce MAC, not to directly form the MAC itself. It does not activate B cells via CD40.