The alternative pathway of complement activation has an important role in innate immunity, due to its ability to greatly amplify the amount of C3b deposited onto the pathogen surface. This amplification occurs because:
A) The C3 convertase of the alternative pathway is much more active than those of the classical and lectin pathways.
B) The C3 convertase of the alternative pathway works as a soluble enzyme in the plasma.
C) The C3 convertase of the alternative pathway cannot be inactivated by complement regulatory factors in the host.
D) The C3 convertase of the alternative pathway is more efficiently recruited to pathogen surfaces than the C3 convertases of the classical and lectin pathways.
E) The C3 convertase of the alternative pathway contains C3b, and can generate more of itself.

Question

Quizplus · Accepted Answer

The C3 convertase of the alternative pathway (C3bBb) is more efficiently recruited to pathogen surfaces than the C3 convertases of the classical and lectin pathways, allowing for more deposition of C3b onto the pathogen surface and amplification of complement activation. This is because the alternative pathway can be activated by spontaneous hydrolysis of C3, allowing for immediate recruitment of C3b to the pathogen surface, whereas the classical and lectin pathways require binding of specific recognition molecules to the pathogen surface before activation can occur.

The Alternative Pathway of Complement Activation Has an Important Role