The tonsils, sets of lymphoid organs oriented toward the digestive tract, are the first defense of the immune system against foreign pathogens and help prevent respiratory and gastrointestinal infections. The tonsils include the adenoid tonsil, two tubal tonsils, two palatine tonsils and the lingual tonsils. The tonsils have specialized antigen-capturing cells on their surface, called M-cells, which help to absorb antigens produced by pathogens. These M cells then alert the underlying B and T cells in the tonsil to the presence of a pathogen and an immune response is stimulated. Endothelial cells, epithelial cells, and fibroblasts are essential components necessary for normal functioning of the tonsil system. Changes in cell proliferation and regulation within the tonsil system lead to the development of tonsillitis and adenotonsillar hyperplasia.