Question

Which of the following factors are required for complement activation by alternative pathway:

• A. C1, factor B, factor D and properdin
• B. C2, factor B, factor D and properdin
• C. C3, factor B, factor D and properdin
• D. Lectin, factor B, factor D and properdin

Hint:

Alternative = “ABDP” (Alternative uses B, D, and Properdin starting with C3).

Answer 1

The Correct Option is C

Step 1: Concept
The complement system's alternative pathway is one of three activation pathways.

Step 2: Meaning
Unlike the classical pathway, it does not require antibodies.

Step 3: Analysis
The alternative pathway begins with spontaneous hydrolysis of C3, and requires Factor B, Factor D, and Properdin. C1/C2 belong to the classical pathway; Lectin belongs to the MBL pathway.

Step 4: Conclusion
C3, B, D, and properdin are the defining factors.

Final Answer: (C)