| The microfold cells (M cells) of the gut are modified epithelial cells which make antigenic material more readily available to the immune system. Seen here in the mucosa between the enterocytes with microvilli, above the basement membrane, is a microfold cell. The microfold cell can phagocytize antigenic material, including bacteria and macromolecules. After endocytosis, the antigenic material is transported in a vesicle to the base of the M cell, where exocytosis releases the material to a lymphocyte or macrophage that can occupy a large invagination of the M cell's basal membrane. Additional immune cells, including lymphocytes as well as macrophages are present in submucosa, often in a lymphoid nodule or Peyer's patch. The immune cells process the antigen to aid in immunologic defense mechanisms. |