Question

Which of the following statements about IgA is/are correct?

• A. It is secreted into colostrum.
• B. It is transported across the cell by transcytosis.
• C. Its secretion is facilitated by poly-Ig receptor.
• D. It primarily exists as a dimer in serum.

Hint:

IgA is crucial for mucosal immunity, secreted into colostrum, and transported across epithelial cells through transcytosis, aided by the poly-Ig receptor.

Answer 1

The Correct Option is A, B, C

Step 1: Understanding IgA functions.
Immunoglobulin A (IgA) plays a critical role in mucosal immunity. It is secreted into colostrum (the first form of breast milk), helping protect neonates from infections. IgA is transported across epithelial cells via transcytosis, which allows it to reach mucosal surfaces. The poly-Ig receptor facilitates its secretion across epithelial cells. Additionally, IgA predominantly exists as a dimer in serum, forming a secretory form when secreted into mucosal surfaces.

Step 2: Analyzing the options.
- (A) It is secreted into colostrum: Correct, as IgA is secreted into colostrum to protect newborns.
- (B) It is transported across the cell by transcytosis: Correct, as this is the process that helps IgA move across mucosal cells.
- (C) Its secretion is facilitated by poly-Ig receptor: Correct, as this receptor helps in the transport of IgA.
- (D) It primarily exists as a dimer in serum: Incorrect, as IgA exists as a dimer when secreted, but in serum, it exists as a monomer.

Step 3: Conclusion.
The correct answers are (A), (B), and (C), as they correctly describe the functions of IgA.