Peyerplakkok

Peyer’s patches, also known as Peyer’s plaques or aggregated lymphoid nodules, are clusters of lymphoid tissue found in the ileum, the final section of the small intestine in the human digestive system. Named after the Swiss anatomist Wilhelm Peyer, who first described them in the 17th century, these structures play a crucial role in the immune response within the gastrointestinal tract.

Peyer’s patches are composed of multiple lymphoid follicles, each containing B lymphocytes, T lymphocytes, macrophages, and other immune cells. They are strategically located beneath the intestinal epithelium, allowing them to monitor and respond to antigens present in the gut lumen. Unlike other lymphoid tissues, Peyer’s patches lack a fibrous capsule and are not encapsulated, making them appear as diffuse patches along the intestinal wall.

Their primary function is to sample and initiate immune responses against pathogens, such as bacteria and viruses, that enter the digestive system. The specialized epithelial cells overlying Peyer’s patches, called M cells (microfold cells), facilitate the transport of antigens from the gut lumen into the underlying lymphoid tissue, where immune activation occurs. This process helps prevent the establishment of infections while maintaining tolerance to commensal bacteria and dietary antigens.

In addition to their role in pathogen defense, Peyer’s patches contribute to the regulation of immune homeostasis in the gut. They participate in the development of mucosal immunity by promoting the differentiation of B cells into immunoglobulin A (IgA)-producing plasma cells, which are essential for protecting mucosal surfaces. Dysfunction or dysregulation of Peyer’s patches has been linked to various gastrointestinal and systemic immune disorders, including inflammatory bowel disease and autoimmune conditions.