Peyer's patches are located in which tissue?

• A. Nervous tissue in the brain
• B. Lymphoid tissue in the gut wall with high metabolism
• C. Glandular tissue in the stomach
• D. Muscle tissue in the intestine

Answer: (B)

Peyer's patches are part of gut-associated lymphoid tissue and sit in the mucosa and submucosa of the small intestine, especially the ileum. They are organized lymphoid follicles rich in B cells, T cells, dendritic cells, and macrophages, reflecting their role in immune surveillance of intestinal contents. Antigen sampling is aided by specialized M cells that transport luminal antigens to underlying immune cells, triggering immune activation and IgA production. This activity requires high cellular metabolism due to ongoing lymphocyte proliferation and antigen processing, which is why they are described as lymphoid tissue in the gut wall with high metabolic activity. They are not nervous tissue in the brain, glandular tissue in the stomach, or muscle tissue in the intestine.