ARS | Publication request: Examination of the reticular epithelium of the bovine pharyngeal tonsil

Submitted to: The Anatomical Record
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 14, 2011
Publication Date: August 1, 2011
Citation: Palmer, M.V., Stasko, J.A., Waters, W.R., Thacker, T.C. 2011. Examination of the reticular epithelium of the bovine pharyngeal tonsil. The Anatomical Record. 294(11):1939-1950.

Interpretive Summary: The tonsils are located at the back of the throat in a position where they can monitor foreign substances that enter through either the mouth or nose. Entering foreign material will first contact the surface layer of the tonsils. We examined the tonsils (adenoids) of cattle and determined that the tonsil surface layer contains many cells that are important in initiating an immune response to a foreign agent, such as bacteria or viruses. A better understanding of the structure and function of tonsils will help understand disease transmission and progression, as well the potential use of oral or intranasal vaccines.

Technical Abstract: The nasopharyngeal tonsil (adenoid), located at the posterior of the nasopharynx is ideally positioned to sample antigens entering through the nasal cavity or oral cavity. Entering antigens will first contact tonsilar epithelium. To better understand the cellular composition of this important epithelial layer, nasopharyngeal tonsils were collected from six, 7-month-old calves and examined by light microscopy, immunohistochemistry and electron microscopy. Morphometric analysis showed that epithelium overlying lymphoid follicles (reticular epithelium) contained significantly more B-cells, CD4+, and CD11c+ cells than non-reticular epithelium. In contrast, non-reticular epithelium contained significantly more, g/d TCR+ cells than reticular epithelium. Scanning and transmission electron microscopy of reticular epithelium identified a heterogeneous population of epithelial cells, many of which displayed characteristics of M-cells. Bovine nasopharyngeal tonsilar reticular epithelium contains key immune cells, as well as M cells, elements essential for antigen uptake, antigen processing and initiation of immune responses. A better understanding of the morphology and function of the nasopharyngeal tonsil, as well as other tonsils, will strengthen our understanding of their role in disease pathogenesis, and their potential use as an induction site for mucosal immune responses to intranasal vaccines.