Digestive tract lymphoid tissue of poultry

Digestive system is protected by many defensive mechanisms installed along the canal because digestive tract exposed to plenty of pathogenic microorganisms and harmful substances. In chickens which is devoid of mammalian type lymph nodes, digestive tract lymphoid tissue (GALT) and spleen are important regions in the formation and conclusion of immunological responses. GALT is shaped by immune cells which spreading to the epithelial layer and the lamina propria of gastrointestinal tract in chickens. In addition, there are structures and lymphoid cell populations which is localized to various locations throughout the digestive system. Farengeal tonsil, oesophageal tonsil, pyloric tonsil, Meckel’s diverticulum, caecal tonsil, Peyer’s patches and bursa of Fabricius which are scatterly throughout lamina propria and intraepithelium of digestive system of poultry are important lymphoid formations which play role in microbial defense. In poultry, oculonasal region containing many lymphoid tissue associated with lacrimal gland, Harderian gland and nasal gland is functioning as an insurance of immune system at the onset of the digestive system with esophageal tonsils. This lymphoid tissues of the gastrointestinal tract are permanent structures. In this review, it is aimed to be a resource for studies planned to be done by giving information about digestive tract lymphoid tissue of poultry.