Question

Which immunoglobulin is primarily responsible for mucosal immunity?

• A. IgM
• B. IgG
• C. IgA
• D. IgD

Hint:

Use mnemonics for primary antibody functions: \textbf{A} for \textbf{A}way/secretions (mucosal), \textbf{G} for \textbf{G}eneral/most abundant (serum), \textbf{M} for \textbf{M}acro/first responder, \textbf{E} for \textbf{E}osinophils/All\textbf{e}rgy.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Immunoglobulins (antibodies) are classified into distinct isotypes (IgM, IgG, IgA, IgE, IgD), each serving unique roles and predominating in different locations within the body.

Step 2: Detailed Explanation:
Let's review the primary function of each given isotype.
- IgA: Secretory IgA is the most abundant immunoglobulin in mucous secretions such as tears, saliva, colostrum, and secretions of the respiratory and intestinal tracts.
It plays a critical role in mucosal immunity by neutralizing pathogens before they can cross the mucosal barrier.
- IgM: This is the first antibody produced in a primary immune response and is mainly found in the blood.
- IgG: This is the most abundant antibody in serum, responsible for long-term systemic immunity, and it can cross the placenta.
- IgD: This primarily functions as an antigen receptor on the surface of naive B cells.

Step 3: Final Answer:
Because IgA is the predominant antibody found in mucosal secretions, it is the correct answer.
Therefore, the correct option is (C).