| Part1Enhanced transepithelial antigen transport in nasal epithelium of allergic rhinitis patients is mediated by IgE and CD23Background:For inhaled allergens to gain access to immune effector cells in the lamina propria, they must first cross the nasal epithelium containing ciliated columnar and mucus-secreting goblet cells.These cells can form a highly regulated and impermeable barrier made possible through the formation of tight junctions localized in the apical part of the columnar cells. In general, tight junctions prevent the free uptake and passage of macromolecules such as IgE and allergens. Hence, the exact mechanisms responsible for the cross-talk between allergen/IgE and immune effector cells in the airway remains poorly understood. Several elegant studies have demonstrated a potential function for CD23to transport IgE and IgE-derived immune complex (IC) across the polarized human intestinal epithelial monolayer. Furthermore, the facilitated transport of IgE and uptake of Ags by CD23are essential steps in the initiation of rapid allergic in-flammation in the intestine in a murine model. However, it remains completely unknown whether a similar mechanism of transport of IgE or IC exists in nasal epithelium.Objectives:The present study was designed to detect the expression of CD23protein in nasal mucosa of allergic rhinitis patients, and to investigate whether CD23was capable of transporting human IgE or IgE-derived IC across primary human nasal epithelial monolayers.Main methods:Nasal inferior turbinate tissue were collected from subjects suffered with nasal septum deviation and allergic rhinitis, who need remove partial inferior turbinate to improve breathing, undergoing functional endoscopic sinus surgery. The control specimens included inferior turbinate tissue from individuals without history of allergic rhinitis or asthma who were undergoing sinonasal surgery for unrelated reasons (eg, skull base tumor, cerebrospinal fluid rhinorrhea). The CD23expression in nasal mucosa tissue was detected by immunohistochemistry and western blotting. Hybridization in situ was used to detected CD23a and CD23b mRNA. Primary cultured human nasal epithelial cells were identified by the expression of pan Keratin. The CD23expression in primary cultured human nasal epithelial cells was detected by immunohistochemistry and western blotting. Next primary nasal epithelial cells were cultured on permeable supports, and formed epithelial cell monolayers. Transport of IgE and IC were measured across epithelial cell monolayers, either primary AR patients’ nasal epithelial cells or nomal comtrol patients’, or in the presence of blocking antibody.Results:CD23was constitutively expressed in human nasal epithelial cells, and its expression was significantly up-regulated in AR patients. Immunofluorescence show that the colocalization of CD23and IgE was observed in both the apical and the basolateral region of nasal epithelial cells in the AR patients, whereas was less detectable in normal control patients. Hybridization in situ showed CD23a and CD23b mRNA were expressed in nasal epithelial cells of all patients. The staining level of CD23a and CD23b mRNA of allergic rhinitis patients were significantly’higher than that of nomal control. Immunocytochemistry and Western Blot showed that CD23was constitutively expressed in primary cultured human nasal epithelial cells, and its expression was significantly up-regulated in primary cultured nasal epithelial cells of AR patients. In a transcytosis assay, human IgE or IgE-derived immune complex (IC) was transported across monolayer of primary cultured human nasal epithelial cells. The transcytosis of either human IgE or the IC was enhanced in the monolayer of primary cultured human nasal epithelial cells of AR patients. A CD23-specific Ab or soluble CD23significantly reduced the efficiency of IgE or IC transcytosis, suggesting a specific receptor-mediated transport by CD23.Conclusions:IgE bound to low-affinity receptors CD23on nasal epithelial cells are responsible for the specific antigen transport system, which is enhanced in allergic rhinitis patients.Part2In vivo intranasal anti-CD23treatment inhibits allergic responses in a murine model of allergic rhinitisObjectives:Our study showed that CD23on human nasal epithelial cells played a pivotal role in transporting IgE and allergen-IgE complexes across the airway epithelial cell barrier in vitro. The present study was designed to detect the expression of CD23protein in nasal mucosa of allergic rhinitis (AR) murine model, and to investigate whether blocking CD23-dependent transepithelial transcytosis via intranasal anti-CD23treatment could inhibit allergen-induced upper airway inflammation in AR murine model.Main methods:The murine model of allergic rhinitis was established by sensitized and intranasally challenged with ovalbumin. The CD23expression in nasal mucosa was detected by immunohistochemistry and western blotting. Intranasal anti-CD23treatment was used to block CD23-dependent transcytosis. After treatment, we evaluated nasal symptom and histopathology of the mice. Meanwhile, levels of ovalbumin-specific IgE (OVA-specific IgE), leukotriene C4(LTC4), IL-4, and eosinophil cation protein (ECP) in serum, and levels of OVA-specific IgE and LTC4in nasal lavage fluid (NLF) were detected by ELISA. Furthermore, ECP expression in nasal mucosa was also detected by western blotting. Finally, the phenotype of CD4+T cells from the spleen was assayed by flow cytometry.Results:CD23was constitutively expressed in murine nasal epithelial cells, and its expression was significantly up-regulated in AR murine model. In vivo the rise in CD23expression was correlated with the increased serum IL-4levels, and positive correlation between CD23expression in nasal mucosa and the IgE titers in NLF also reached statistical significance. After anti-CD23treatment, nasal symptoms were alleviated; Histopathologic examination showed eosinophilic infiltration significantly decreased; ELISA assay showed levels of serum LTC4, ECP, OVA-specific IgE and IL-4also significantly decreased, as were LTC4and OVA-specific IgE in the NLF; And Western Blotting showed that ECP expression in nasal mucosa declined. These results indicated that in vivo blockage of CD23-dependent transport across nasal epithelial cells by intranasal anti-CD23treatment inhibited allergic responses in a murine model of AR.Conclusions:Our study indicates that CD23-dependent transepithelial transcytosis of IgE and allergen-IgE complex may play a pivotal role in the initiation and development of nasal allergic inflammation, and the blockage of CD23-mediated transport across nasal epithelial cells could be a novel therapeutic strategy for allergic rhinitis. |
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