The alternative complement pathway is triggered:

• A. exclusively during viral infections
• B. by direct interaction with pathogen surfaces, independent of antibodies
• C. by the binding of mannose-binding lectin to microbial carbohydrates
• D. only after antibodies bind to antigens

Answer: (B)

Verified step by step guidance

1. Understand that the complement system has three activation pathways: classical, lectin, and alternative.
2. Recall that the classical pathway is triggered by antibodies bound to antigens, so it is antibody-dependent.
3. Know that the lectin pathway is initiated by mannose-binding lectin binding to specific carbohydrates on microbial surfaces.
4. Recognize that the alternative pathway is unique because it is activated directly by pathogen surfaces without the need for antibodies or lectins.
5. Conclude that the alternative complement pathway is triggered by direct interaction with pathogen surfaces, independent of antibodies.