Distribution of Lysozyme-and Lactoferrin-Secreting Cells in Eustachian Tube of Normal BALB/c Mouse

Abstract

BACKGROUND AND OBJECTIVES: Mucosal surfaces in the middle ear and eustachian tube are protected by several complex defense mechanisms, namely mucociliary clearance, immunoglobulins, cellular components, and antibacterial secretory enzymes. The secretory enzymes such as lysozyme and lactoferrin are found in various mucosal tissues and most of body secretions which cover the human mucosal surfaces. Because of their bactericidal activity, it has been suggested that these enzymes contribute to the defense against local mucosal infections. It has been known that lysozyme- and lactoferrin-secreting cells in tubotympanum were various in species such as human, chinchilla, guinea pig and Mongolian gerbil. The purpose of this study is to identify and localize the lysozyme- and lactoferrin-secreting cells in the eustachian tube of normal mice using histochemical and immunohistochemical techniques. MATERIALS AND METHODS: Normal mice (BALB/c, 60-120 days old, 10 heads) were used for staining of tubotympanum with hematoxylin-eosin stain, Alcian blue-periodic acid-Schiff (AB-PAS) stain and immunohistochemical stain (antihuman lysozyme, and antihuman lactoferrin antibodies). RESULTS: 1) Secretory cells in the epithelium and subepithelial glands are observed more in the pharyngeal portion than in the tympanic portion of eustachian tube. Subepithelial glands are also noted more in lower part than in upper part of eustachian tube. 2) Lysozyme was observed in the secreting cells of mucosal epithelium and the serous cells of subepithelial glands. 3) Lactoferrin was observed in the serous cells of subepithelial glands, but not in the epithelium. CONCLUSION: In the eustachian tube of BALB/c mouse, lysozyme and lactoferrin were detected in the serous cells in subepithelial glands and only lysozyme is observed in the secretory cells in the eustachian tube epithelium.