Microfold Cells

Microfold  Cells or M Cells

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.

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

an immune response or tolerance

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

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.

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.

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.