In mucosal immunity of the small intestine, what is the primary role of specialized microfold (M) cells located over Peyer’s patches?

Introduction / Context:
M cells are specialized epithelial cells that overlay Peyer’s patches in the gut-associated lymphoid tissue (GALT). They are crucial for sampling luminal antigens and initiating mucosal immune responses. Understanding their function helps explain oral tolerance and mucosal vaccine strategies.

Given Data / Assumptions:

• Location: Follicle-associated epithelium of the ileum.
• Function: Antigen sampling and delivery to immune cells.

Concept / Approach:
M cells lack a thick brush border and mucus production; instead, they efficiently endocytose or phagocytose luminal particles and deliver them via transcytosis to the immune cell–rich basolateral pocket containing macrophages and dendritic cells. This promotes antigen presentation and activation of B and T cells.

Step-by-Step Solution:

Verification / Alternative check:
Histology shows M-cell basolateral pockets with immune cells. Oral vaccines (e.g., live attenuated) exploit this pathway for uptake.

Why Other Options Are Wrong:

• Mucus trapping and ciliary propulsion: Functions of goblet and ciliated respiratory epithelium, not intestinal M cells.
• Apoptosis induction: Not the primary role of M cells.
• IgA secretion: Plasma cells in lamina propria secrete IgA, which is transported across enterocytes via pIgR.

Common Pitfalls:

• Confusing M cells with enterocytes or goblet cells.
• Assuming all mucosal epithelial cells have similar roles.

Final Answer:
Transcytose microbes to underlying macrophages/dendritic cells for processing and antigen presentation