Abstract
As the main mucosal immune inductive site of nasal cavity, nasal-associated lymphoid tissue (NALT) plays an important role in both antigen recognition and immune activation after intranasal immunization. However, the efficiency of intranasal vaccines is commonly restricted by the insufficient intake of antigen by the nasal mucosa, resulting from the nasal mucosal barrier and the nasal mucociliary clearance. The distribution of NALT and the characteristic of nasal cavity have already been described in humans and many laboratory rodents, while data about poultry are scarce. For this purpose, histological sections of the chicken nasal cavities were used to examine the anatomical structure and histological characteristics of nasal cavity. Besides, the absorptive capacity of chicken nasal mucosa was also studied using the materials with different particle size. Results showed that the NALT of chicken was located on the bottom of nasal septum and both sides of choanal cleft, which mainly consisted of second lymphoid follicle. A large number of lymphocytes were distributed under the mucosal epithelium of inferior nasal meatus. In addition, there were also diffuse lymphoid tissues located under the epithelium of the concha nasalis media and the walls of nasal cavity. The results of absorption experiment showed that the chicken nasal mucosa was capable to absorb trypan blue, OVA, and fluorescent latex particles. Inactivated avian influenza virus (IAIV) could be taken up by chicken nasal mucosa except for the stratified squamous epithelium sites located on the forepart of nasal cavity. The intake of IAIV by NALT was greater than that of the nasal mucosa covering on non-lymphoid tissue, which could be further enhanced after intranasal inoculation combined with sodium cholate or CpG DNA. The study on NALT and nasal absorptive capacity will be benefit for further understanding of immune mechanisms after nasal vaccination and development of nasal vaccines for poultry.
Highlights
Mucosal vaccination is a promising alternative to parenteral vaccination, as it is noninvasive and, in principle, capable of eliciting strong local and systemic immune responses in mucosalassociated lymphoid tissue (MALT)
Lymphoid nodules were the major Nasal-associated lymphoid tissues (NALT) structures in chickens. They were composed of B cells with frequently developed germinal centers (GC), surrounded by a coat of CD4+ cells, while CD8+ cells were located in the epithelium and in the lamina propria of the nasal cavity mucosa [6,7]
The bracket of the nasal abdominal walls was composed of the palatine process of the maxilla and frontal bone, while the posterior part of the nasal cavity was mainly made up of parenchyma and was underpropped by the palatine bone and the vomer
Summary
Mucosal vaccination is a promising alternative to parenteral vaccination, as it is noninvasive and, in principle, capable of eliciting strong local and systemic immune responses in mucosalassociated lymphoid tissue (MALT). Among the mucosal administration sites, nasal cavity may be the most attractive one. Nasal-associated lymphoid tissues (NALT) are considered as the main inductive sites for immune responses in both natural infection and vaccination [2,3]. Lymphoid nodules were the major NALT structures in chickens. They were composed of B cells with frequently developed germinal centers (GC), surrounded by a coat of CD4+ cells, while CD8+ cells were located in the epithelium and in the lamina propria of the nasal cavity mucosa [6,7]. Bronchusassociated lymphoid tissue (BALT), constitutively present in normal chicken lungs [8], has the similar structures with NALT. Its structures showed features characteristic for mucosal inductive sites [2,10]. The location and histological structure of NALT in chicken were not investigated systematically and detailedly
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