Question

Consider the following: 1. Rise in the level of IgA. 2. Fall in the level of opsonin. Which of these is/are the immunological change(s) following splenectomy?

• A. 1 only
• B. 2 only
• C. Both 1 and 2
• D. Neither 1 nor 2

Hint:

Recall which antibody class the spleen actually produces, and what opsonins do.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question lists two possible immunological changes after splenectomy — a rise in IgA and a fall in opsonin — and asks which of them actually occurs.

Step 2: Key Concept or Approach:
The spleen is a major site of IgM production (the early antibody response to blood-borne antigens) and it houses macrophages that manufacture opsonins, including tuftsin and properdin, which coat encapsulated bacteria and mark them for phagocytosis. IgA, by contrast, is produced mainly by mucosa-associated lymphoid tissue in the gut and respiratory tract, not by the spleen, so splenectomy does not raise IgA levels.

Step 3: Working Through the Options:
After splenectomy, IgM tends to fall rather than rise, and opsonin levels (tuftsin, properdin) fall because the spleen is a key source of them; this fall in opsonins explains the marked susceptibility to encapsulated organisms such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis, known as overwhelming post-splenectomy infection (OPSI). IgA is essentially unaffected and does not rise, so statement 1 is false. Statement 2, the fall in opsonin, is true. "1 only" and "Both 1 and 2" are wrong because they include the false IgA claim, and "Neither 1 nor 2" is wrong because it denies the true opsonin fall.

Step 4: Conclusion:
Only statement 2 is correct — splenectomy causes a fall in opsonin level.