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Complement System — NDEB AFK MCQ

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HardBiomedical SciencesComplement SystemNDEB AFK

Which pathway is primarily responsible for activating the complement system in the early stages of bacterial infection, without prior antibody exposure?

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Correct answer: A — Alternative pathway

The alternative pathway of complement is activated spontaneously by C3 hydrolysis and is amplified on microbial surfaces lacking regulatory proteins. It does not require antibody and provides immediate innate defence. The classical pathway requires antigen-antibody complexes. The lectin pathway requires mannose-binding lectin binding to microbial surfaces.

Reference: Abbas – Cellular and Molecular Immunology, 10th ed., 2021