The Waldeyer's ring.

The palatine tonsils, nasopharyngeal tonsil (adenoid) and lingual tonsil constitute the major part of Waldeyer's ring or nasal-associated lymphoid tissue (NALT), with the tubal tonsils and lateral pharyngeal bands as less prominent components. The lymphoid tissue of Waldeyer's ring is located at the gateway of the respiratory and alimentary tract and belongs to the mucosa-associated lymphoid tissue (MALT). As tonsils are the first site of encounter with inhaled and ingested micro-organisms, they are considered the first line of defense against exogenous aggressors. The generation of B cells in the germinal centers of the tonsil is one of the most essential tonsillar functions. This manuscript aims to review the anatomy and current knowledge on the immunologic function of the Waldeyer's ring.