Peyersche

Peyersche, in English usually referred to as Peyer’s patches, are organized lymphoid aggregates that form part of the gut-associated lymphoid tissue (GALT) in the ileum. They are named after the Swiss anatomist Johann Conrad Peyer. These lymphoid nodules are located predominantly in the distal ileum, extending into the submucosa and lamina propria as discrete patches. In the terminal ileum, dozens of Peyer’s patches can be present, and together they contribute to mucosal immune surveillance.

Structurally, each patch comprises lymphoid follicles with B cell–rich germinal centers and surrounding T cell zones. The surface covering of a Peyer’s patch is the follicle-associated epithelium, which contains specialized M cells. M cells sample antigens from the intestinal lumen and transport them to underlying immune cells, facilitating antigen presentation and initiation of immune responses. The patches communicate with the broader immune system via afferent lymphatics that drain to mesenteric lymph nodes and, ultimately, the systemic circulation.

Functionally, Peyer’s patches play a key role in recognizing luminal antigens, initiating adaptive immune responses, and promoting the production of IgA-secreting plasma cells. They contribute to mucosal immunity and tolerance to dietary antigens and commensal microbes, while also participating in the development of local memory B and T cells.

Development and clinical relevance vary with age and health. Peyer’s patches are present in late fetal life and expand in infancy and childhood; they can show hyperplasia during infection. Pathogens such as Salmonella typhi can invade via M cells in Peyer’s patches, illustrating their role in intestinal entry for certain organisms.