The complement system is activated via three pathways:

A Only one pathway

B Classical (antibody-antigen), lectin (mannose), and alternative (C3 tickover) pathways

C Only innate immunity

D Antibody pathway only

✓ Correct Answer: Option B

Complement activation: Classical (C1q binds Ab-Ag complex), Lectin (MBL binds mannose on pathogen), Alternative (spontaneous C3 hydrolysis). All converge at C3 convertase → MAC (C5b-9).

💡 Why is B) the correct answer?

The correct answer to the question "The complement system is activated via three pathways:" is Option B: Classical (antibody-antigen), lectin (mannose), and alternative (C3 tickover) pathways.

The other options — A) Only one pathway, C) Only innate immunity, D) Antibody pathway only — are incorrect for this USMLE Exam Prep question. As explained above: Complement activation: Classical (C1q binds Ab-Ag complex), Lectin (MBL binds mannose on pathogen), Alternative (spontaneous C3 hydrolysis). All converge at C3 convertase → MAC (C5b-9).

📚 About This USMLE Exam Prep Practice Question

This 3-level USMLE Exam Prep question from the Step 1 - Basic Sciences topic is part of BrainForge Quiz's free exam preparation library. Each question includes the correct answer and a detailed explanation to help you understand the underlying concept, not just memorize the answer.

How to use this page: Read the question above, consider all four options (A through D), then check the highlighted correct answer and explanation. For active timed practice, start a free USMLE Exam Prep practice test or use flashcards for spaced repetition review.

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The complement system is activated via three pathways:

✓ Correct Answer: Option B

📚 About This USMLE Exam Prep Practice Question

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