Characterization of nasal cavity-associated lymphoid tissue in ducks.

The nasal mucosa is involved in immune defense, as it is the first barrier for pathogens entering the body through the respiratory tract. The nasal cavity-associated lymphoid tissue (NALT), which is found in the mucosa of the nasal cavity, is considered to be the main mucosal immune inductive site in the upper respiratory tract. NALT has been found in humans and many mammals, which contributes to local and systemic immune responses after intranasal vaccination. However, there are very few data on NALT in avian species, especially waterfowl. For this study, histological sections of the nasal cavities of Cherry Valley ducks were used to examine the anatomical location and histological characteristics of NALT. The results showed that several lymphoid aggregates are present in the ventral wall of the nasal cavity near the choanal cleft, whereas several more lymphoid aggregates were located on both sides of the nasal septum. In addition, randomly distributed intraepithelial lymphocytes and isolated lymphoid follicles were observed in the regio respiratoria of the nasal cavity. There were also a few lymphoid aggregates located in the lamina propria of the regio vestibularis, which was covered with a stratified squamous epithelium. This study focused on the anatomic and histological characteristics of the nasal cavity of the duck and performed a systemic overview of NALT. This will be beneficial for further understanding of immune mechanisms after nasal vaccination and the development of effective nasal vaccines for waterfowls.