Ileum with Peyer's patches ('gut-associated lymphatic tissue' or GALT) (human)

Stain: Azan. Survey ileum (see also Digestive System: Ileum) A large amount of non-encapsulated diffuse lymphatic tissue or mucosa-associated lymphatic tissue (MALT) is located in the subepithelial lamina propria/submucosa of the ileum and called 'gut-associated lymphatic tissue' (GALT). These so-called Peyer' patches are large aggregations of lymphatic nodules (1) (about 200-400 nodules) extending from the proper lamina (2) into the submucosa (3). The nodules with germinal centres (1) are similar to those found in the lymph node with darker-stained caps (4) orientated towards the lining cylindrical epithelium (5); (6) intestinal villi; (--> short crypts of Lieberkhn); (8) muscular layer. Dome areas (9) bulge from the lymphatic tissue of the submucosa into the intestinal lumen. Here, the epithelium of the dome areas does not display microvilli or crypts or mucous-producing goblet cells. Instead of microvilli these specialized epithelial cells show micro folds at their surfaces (micro fold cells or M-cells). These M-cells function as antigen-transporter cells towards the underlying follicles. T cells are mostly spread in the interfollicular regions. The follicles mainly contain B cells