Microfold Cells

Where the M Cells present?

Microfold  Cells or M Cells are present in follicle-associated epithelium (FAE)

Follicle -associated epithelium is a specialized epithelium present over  Peyer’s  patch in small intestine and isolated lymphoid follicles.

M cells are seen in epithelial cells of the mucosa-associated lymphoid tissues.

Microfold cells (or M cells) are found in the gut-associated lymphoid tissue (GALT) of the Peyer's patches in the small intestine, and in the mucosa-associated lymphoid tissue (MALT) of other parts of the gastrointestinal tract.

	Microfold cells (or M cells) are found
1	GALT - Gut-associated lymphoid tissue	Peyer's patches in the small intestine
2	MALT - Mucosa-associated lymphoid tissue	Other parts of the gastrointestinal tract.

What is function of the M Cells?

M cells helps to transport antigens from intestinal lumen to  immune system cells, and starts

an immune response or tolerance.

M cells function are phagocytosis and transcytosis. M cells are capable of taking up large particulate antigens from the lumen and transporting them intact into the subepithelial space.

	Function of the M Cells
1	Initiate mucosal immunity responses on the apical membrane of the M cells
2	Transport of microbes and taking up large particulate antigens from the gut lumen to the lamina propria [For interactions with immune cells]

What is function of the M Cells in polio virus infection?

M cells express lectin-like molecules in the apical surface. These molecules  help to promote binding to specific pathogens such as poliovirus.

What is the mechanism where M cells involved with IgA response in payer patches?

Antigens that bind to the M cell and are transported to the underlying Peyer patches generally elicit a positive (IgA) response.

M cell helps to connect  Peyer patches and lymphoid follicles as conduit.

Once antigens enter the Peyer patch, TGF-β-secreting T cells promote B cell isotype switching to IgA.

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If Peyer patch B cells are absent then  M cells are also absent. [M cells have not seen in B cell–deficient animals, which lack Peyer patches]

Peyer  patches have T cell-dependent areas and B cell-dependent/germinal centers typical of lymph nodes, but only efferent lymphatics.