Esophageal tonsil: a novel gut-associated lymphoid organ

Abstract

The esophageal tonsil of the chicken is a novel, significant element of the gut-associated lymphoid tissue (GALT). Its stable location and histological organization fulfills the meaning of the term "tonsil." The six-to-eight-isolated tonsillar units are located at the border of the esophagus and the proventriculus. The number of tonsillar units is identical with that of the esophageal folds. Each tonsillar unit consists of a crypt lined by lymphoepithelium and surrounded by dense lymphoid tissue, which is organized into T- and B-dependent regions, like peripheral lymphoid organs. The excretory ducts of the mucosal glands of the esophagus are frequently involved in the formation of the lymphoepithelium. The esophageal tonsil is anatomically located cranial to the stomach, unlike the other parts of the GALT. Therefore, it is continuously exposed to undigested environmental antigens, allergens, food, and infectious agents. To develop effective oral vaccines, the existence of the esophageal tonsil has to be taken into account.

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

“…The lymphoid tissue is composed of either scattered or aggregated lymphoid cells, or is well organized into primary and secondary lymphoid follicles that are separated by interfollicular aggregations of lymphoid cells (Ogra, 2000). At some strategic anatomical locations, the lymphoid tissue is organized into tonsils (Oláh et al, 2003;Anonymous, 2005). The latter are complex lymphoid organs that often contain crypts which are lined by a lympho-epithelium (Oláh et al, 2003).…”

“…At some strategic anatomical locations, the lymphoid tissue is organized into tonsils (Oláh et al, 2003;Anonymous, 2005). The latter are complex lymphoid organs that often contain crypts which are lined by a lympho-epithelium (Oláh et al, 2003).…”

“…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).…”

“…It causes thickening of the oesophageal wall, which is far more obvious in the duck compared with the chicken (Grau-Karlsbad, 1943;Schummer, 1973). According to the number of longitudinal folds in the oesophageal wall, the tonsil is divided into several (up to eight) tonsillar units that are all located in the lamina propria mucosae between two folds (Oláh et al, 2003;Sagsö z & Liman, 2009). Consequently, each tonsillar unit surrounds a crypt (Oláh et al, 2003).…”

“…According to the number of longitudinal folds in the oesophageal wall, the tonsil is divided into several (up to eight) tonsillar units that are all located in the lamina propria mucosae between two folds (Oláh et al, 2003;Sagsö z & Liman, 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.…”