Which of the following statements correctly identifies the C3 convertase of the alternative pathway?

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Multiple Choice

Which of the following statements correctly identifies the C3 convertase of the alternative pathway?

Explanation:
In the alternative pathway, the C3 convertase is formed by C3b bound to Bb (C3bBb). Factor B is recruited to surface-bound C3b and is cleaved by factor D to produce Bb, yielding the active enzyme C3bBb that cleaves additional C3 into C3a and C3b, amplifying the response. On microbial surfaces, this convertase is stabilized by properdin, increasing its half-life. The other options correspond to different complexes: C4b2a is the C3 convertase of the classical/lectin pathways, while C4b2a3b and C3bBbC3b are C5 convertases. Thus, C3bBb correctly identifies the C3 convertase of the alternative pathway.

In the alternative pathway, the C3 convertase is formed by C3b bound to Bb (C3bBb). Factor B is recruited to surface-bound C3b and is cleaved by factor D to produce Bb, yielding the active enzyme C3bBb that cleaves additional C3 into C3a and C3b, amplifying the response. On microbial surfaces, this convertase is stabilized by properdin, increasing its half-life. The other options correspond to different complexes: C4b2a is the C3 convertase of the classical/lectin pathways, while C4b2a3b and C3bBbC3b are C5 convertases. Thus, C3bBb correctly identifies the C3 convertase of the alternative pathway.

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