Peyer Patches

Issues of Concern

The special feature of Peyer patches is that these lymphoid follicles are surrounded by an epithelium known as the follicle-associated epithelium (FAE).[2] This epithelium contains a decreased number of intestinal villi and a thin mucosa layer and is characterized by the presence of epithelial M cells called microfold cells.[3] These M cells are the antigen-presenting cells of the Peyer patches and thus help in their uptake and transport across the intestinal lumen into the bloodstream. The porous nature of the basal lamina of the FAE helps in this antigen-uptaking process.[4]

The Peyer patches contain a significant number of dendritic cells, macrophages, and lymphocytes. Since the gastrointestinal system is exposed to a significant number of pathogens, it is vital for immune surveillance. Once a pathogen is encountered by the M cells in the epithelium, they are presented to the dendritic cells and the macrophages across the membrane via the porous basal lamina, primarily via the transcellular M cell-specific pores.[5] These cells, in turn, activate the lymphocytes, which then travel to the mesenteric lymph nodes, and the amplification of this immune process takes place. The B lymphocytes in the germinal centers are differentiated into immunoglobulin (Ig)A-secreting plasma cells. The produced IgA, along with a protective secretory layer, is then secreted into the lumen to deal with the intraluminal pathogen. T cells in Peyer patches function similarly to LPLs (lipoprotein lipase) and other circulating T cells. However, the distinct feature of these T cells is to secrete tolerogenic cytokines like transforming growth factor (TGF)-beta and interleukin (IL)-10 on exposure to common food allergens, as seen in some animal experiments.

Clinical Significance

In Salmonella typhi infection, intestinal necrosis occurs at the level of the Peyer patches, thereby causing perforation of the distal ileum (in the antimesenteric bowel wall). This most commonly occurs during the third week of febrile illness.[6] Peyer patches are also culprits in the development of idiopathic intussusception. Intussusception most commonly occurs in infants, especially during the weaning period and also due to viral infections like adenovirus in early childhood. This presentation suggests that the exposure of the infant's gut to new pathogens causes the hypertrophy of the Peyer's patches at the lymphoid-rich terminal ileum, resulting in recurrent intussusception or intestinal obstruction.[7][8]

Increased numbers of the Peyer patches also correlate with the development of prions disease, with the M cells uptaking the orally invaded prions and the Peyer patches acting as replicating centers of the prions.[9] However, Peyer patches keep the intestinal flora at appropriate levels and the pathogens at bay, thereby preventing a large number of infections. As a part of the pathogenesis of food allergy, the Peyer patches and vasculature of lamina propria allow the circulation of inflammatory cells to the immune structures.

Nursing, Allied Health, and Interprofessional Team Interventions

The pathologies associated with the functioning and deranged morphology of Peyer patches are important in many gastrointestinal diseases, as seen in the clinical significance. Hence, the appropriate diagnosis and management of these pathologies deal with their timely diagnosis and management. It involves the combined work of the interprofessional team, which includes primary health care clinicians, pathologists/histopathologists, infectious disease specialists, gastroenterologists, and immunologists.