Morphological and phenotypic characteristics of the bovine nasopharyngeal mucosa and associated lymphoid tissue

Authors: MEEK, HAILLIE - Oak Ridge Institute For Science And Education (ORISE); STENFELDT, CAROLINA - Kansas State University; Arzt, Jonathan

Submitted to: Journal of Comparative Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2022
Publication Date: 9/10/2023
Citation: Meek, H.C., Stenfeldt, C., Arzt, J. 2023. Morphological and phenotypic characteristics of the bovine nasopharyngeal mucosa and associated lymphoid tissue. Journal of Comparative Pathology. 198:62-79. https://doi.org/10.1016/j.jcpa.2022.07.011.
DOI: https://doi.org/10.1016/j.jcpa.2022.07.011

Interpretive Summary: This paper describes the microscopic structure and cell types within the nasopharynx of cattle. The nasopharynx is a region in the upper respiratory tract (back of the throat) of all mammals. It is a highly complex region because it lies in the area where the respiratory tract crosses over the gastrointestinal tract. The region contains unique epithelium and abundant lymphoid areas that are important for an animals surveillance of the environment, but which can also be portals of entry for disease agents. In cattle, the nasopharynx is known to be the site of primary infection of foot-and-mouth disease virus (FMDV). This paper describes the unique structures of the nasopharynx of cows with attention to distribution of cells of the immune system including lymphocytes and dendritic cells.

Technical Abstract: The mammalian nasopharynx is an anatomically complex region of the upper respiratory tract that directly communicates with the nasal cavity, laryngopharynx, esophagus, and trachea. The nasopharyngeal mucosa contains moderate quantities of mucosa-associated lymphoid tissue (MALT) that is appropriately located for immunological sampling, but also creates vulnerability to pathogens. In recent years, the nasopharynx has been inculpated in the pathogenesis of high consequence diseases of cattle (foot-and-mouth disease) and humans (COVID-19), yet the tissue has never been described in detail in any species. In order to characterize the morphology and cellular composition of the bovine nasopharynx, samples of mucosa were collected from the nasopharynx of four steers and examined using light microscopy, immunohistochemistry, and multichannel immunofluorescence. Morphologically, the nasopharyngeal epithelium was highly heterogenous, with a continuum ranging from stratified squamous epithelium to highly attenuated, follicle-associated epithelium (FAE). Distribution of MALT was similarly regionally variable ranging from absent to clusters of multiple lymphoid follicles. Phenotypic characterization demonstrated dense distributions of dendritic cells and T lymphocytes surrounding lymphoid follicles, which were comprised of mostly B lymphocytes. The FAE overlaying the lymphoid follicles also contained higher quantities of dendritic cells and lymphocytes compared to the adjacent non-lymphoid epithelium, though cytotoxic T cells were notably scarce in the FAE. The bovine nasopharyngeal lymphoid tissue had comparable elements to other MALTs with specific differences that may help to elucidate the pathogenesis of infectious agents that have specific tropism for this tissue.