Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 20, 2008
Publication Date: February 15, 2009
Citation: Palmer, M.V., Thacker, T.C., Waters, W.R. 2009. Histology, Immunohistochemistry and Ultrastructure of the Bovine Palatine Tonsil with Special Emphasis on Reticular Epithelium. Veterinary Immunology and Immunopathology. 127(3-4):277-285. Interpretive Summary: Tonsils play an important role in several cattle diseases including pneumonia, bovine viral diarrhea, prion diseases, and tuberculosis. To better understand the microscopic anatomy of the tonsils and determine if cells specialized in the uptake of foreign material may be present, tonsils from six 7-month old calves were examined. Microscopic analysis identified a number of critical immune cells in cattle tonsils that could play important roles in the uptake of bacteria and viruses and the initiation of an immune response to those agents. The ability of these cells to capture foreign material was demonstrated using inert latex beads.
Technical Abstract: The paired palatine tonsils are located at the junction of the nasopharynx and oropharynx; ideally positioned to sample antigens entering through either the nasal cavity or oral cavity. Entering antigens will first contact tonsilar epithelium. To better understand the cellular and functional composition of this important epithelial layer, palatine 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 more B-cells, CD4+, CD8+, CD11c+, CD172a+ and gamma/delta TCR+ T-cells than non-reticular epithelium, with B-cells, CD4+ T-cells and CD11c+ T-cells being most numerous. Scanning and transmission electron microscopy identified an interrupted basement membrane and high endothelial venules as well as cells with characteristics consistent with M-cells. Organ culture techniques with latex microspheres demonstrated microparticle uptake by M-cell-like cells. Bovine palatine tonsilar reticular epithelium contains key immune cells, as well as M-cell-like cells, essential for antigen uptake, antigen processing and initiation of immune responses.