Oesophageal tonsil of the chicken

Abstract

The oesophageal tonsil of the chicken is a novel member of the mucosalassociated lymphoid tissue (MALT), which is located around the entrance of the proventriculus. It consists of 6 to 8 single units, which are surrounded by a thin fibrous capsule. Each one is organised around the bottom of the longitudinal folds of the oesophagus, and serves as a 'tonsillar crypt'. Stratified squamous epithelium is infiltrated by lymphoid cells, i.e. T cells, plasma cells, macrophages, and dendritic cells, but not B cells, to form lymphoepithelium (LE). In the LE vimentin-, MHC II-and ATPase-positive cells possibly represent Langerhans' cells, but the appearance of 74.3 positive cells in the LE is unusual, because the 74.3 monoclonal antibody (mAb) recognises chicken follicular dendritic cells in the germinal centre and medulla of the bursal follicles. The subepithelial lymphoid tissue is organised into T-and B-dependent regions, which are the interfollicular areas and the germinal centres, respectively. Existence of high-endothelial venules in the interfollicular region suggests an extensive cellular connection between the oesophageal tonsil and the other lymphoid organs. In the resting oesophagus the lumen is closed, but during swallowing a bolus the crypt opens and the lymphoepithelium can be exposed to undigested food, antigens, infectious agents and vaccines. The location of the oesophageal tonsil, cranial to the stomach, may provide this organ with a unique role as compared to the other parts of the MALT; namely, it may contribute to the replication of infectious bursal disease virus (IBDV) and/or the pathogenesis of infectious bursal disease.

Locations of gut-associated lymphoid tissue in the 3-month-old chicken: a review

“…The oesophageal and pyloric tonsils have recently been studied in detail by means of state-of-the-art techniques (Oláh et al, 2003;Nagy et al, 2005;Nagy & Oláh, 2007). This increasing interest is probably due to the need for solid knowledge about the avian intestinal immune system in the framework of the development of vaccines that have to be administered orally (Nagy et al, 2005).…”

“…The oesophageal and pyloric tonsils have recently been studied in detail by means of state-of-the-art techniques (Oláh et al, 2003;Nagy et al, 2005;Nagy & Oláh, 2007). This increasing interest is probably due to the need for solid knowledge about the avian intestinal immune system in the framework of the development of vaccines that have to be administered orally (Nagy et al, 2005). Moreover, since the ban on growth-promoting antibiotics, research on the avian GALT is impelled by the search for suitable pre-and probiotics that stimulate the intestinal immune system (Yurong et al, 2005;Haghighi et al, 2008;Khan et al, 2008;Janardhana et al, 2009).…”

“…Consequently, each tonsillar unit surrounds a crypt (Oláh et al, 2003). The crypts are lined by a stratified squamous epithelium that is infiltrated by lymphocytes, macrophages and plasma cells, resulting in the formation of a lympho-epithelium that also lines the excretory ducts of the oesophageal mucous glands (Arai et al, 1988;Oláh et al, 2003, Nagy et al, 2005. The function of the lympho-epithelium is, however, not yet known (Oláh et al, 2003).…”

“…2 mm in diameter) separated by interfollicular regions that mainly contain T lymphocytes (Botte & Pelagalli, 1982;Arai et al, 1988;Oláh et al, 2003;Nagy et al, 2005). The presence of high endothelial venules (HEV) within these regions is suggestive of a close immunological association of the oesophageal tonsil with other lymphoid organs (Nagy et al, 2005).…”

“…The presence of high endothelial venules (HEV) within these regions is suggestive of a close immunological association of the oesophageal tonsil with other lymphoid organs (Nagy et al, 2005). Consequently, the avian oesophageal tonsil is part of the common mucosal immune system.…”