Question

The complement system helps the body immunity in following 4 ways. Its correct sequences is: A. Inflammatory reaction, B. Opsonization, C. Complement fixation, D. Clearance of antigen-antibody complexes Choose the correct answer from the options given below:

• A. C, A, D, B \
• B. A, B, C, D \
• C. C, B, A, D \
• D. B, C, D, A

Hint:

The cascade must be "fixed" or anchored to the target surface first (Complement Fixation - C) before it can trigger downstream immune responses like opsonization or inflammation.

Answer 1

The Correct Option is C

Step 1: Concept The complement system is a cascade of plasma proteins that works alongside the immune system to clear pathogens. It can be triggered via three distinct pathways: the classical, alternative, or lectin pathway.

Step 2: Meaning The system operates through an ordered chain of protein cleavages and assemblies, starting from initial activation and leading to downstream immune clearing effects.

Step 3: Analysis *
Step 1: The cascade begins with Complement fixation (C), where complement proteins attach to a pathogen's surface or to an antigen-antibody complex. *
Step 2: Early cleavage steps release fragments like C3b that coat the target pathogen, a process known as Opsonization (B) that makes the pathogen easier for phagocytes to engulf. *
Step 3: Other small fragments released during cleavage (such as C3a and C5a anaphylatoxins) trigger a local Inflammatory reaction (A) by attracting immune cells to the site of infection. *
Step 4: Finally, the system helps clear remaining debris, facilitating the dynamic Clearance of antigen-antibody complexes (D) from the bloodstream.

Step 4: Conclusion The correct functional sequence is C $\rightarrow$ B $\rightarrow$ A $\rightarrow$ D, which corresponds to option C. Final Answer: (C)