Meiqin Wang

Esophageal Remodeling Develops as a Consequence of Tissue Specific IL-5-Induced Eosinophilia

BACKGROUND & AIMS Eosinophilic esophagitis (EE) is an increasingly recognized disease that mimics gastroesophageal reflux disease. Recently, EE has been associated with esophageal remodeling, but the mechanisms involved are poorly understood. We hypothesized that the development of EE in patients and in an experimental murine model would be associated with eosinophil-mediated tissue remodeling. METHODS Histopathologic analysis of basal layer thickness and collagen accumulation was performed on the biopsy specimens of normal individuals, EE patients, and mouse esophageal tissue sections following experimental induction of EE in wild-type, eosinophil lineage-deficient, interleukin (IL)-5-deficient, and IL-5 transgenic mice, with the latter 2 mice groups having decreased and increased esophageal eosinophilia, respectively. RESULTS An impressive accumulation of collagen in the epithelial mucosa and lamina propria, as well as basal layer thickening, was observed in the esophagus of patients with EE as well as in mice with experimental EE compared with controls. Significantly reduced lamina propria collagen and basal layer thickness were observed in IL-5-deficient mice and eosinophil lineage-deficient mice compared with wild-type mice following the induction of experimental EE. Furthermore, the esophagus of CD2-IL-5 transgenic mice showed increased basal layer thickness and collagen accumulation compared with nontransgenic mice, yet IL-5 intestine transgenic mice did not have EE-like esophageal changes. Additional analysis revealed increased IL-5 levels in the esophagus of EE patients, allergen-challenged wild-type mice, and CD2-IL-5 transgenic mice but not in IL-5 intestine transgenic mice. CONCLUSIONS These findings provide evidence that local IL-5-mediated eosinophilia is essential in the induction of esophageal remodeling.

Critical role for adaptive T cell immunity in experimental eosinophilic esophagitis in mice

We have previously developed a murine model of allergen‐induced eosinophilic esophagitis (EE), characterized by intraepithelial eosinophils, extracellular granule deposition, and epithelial cell hyperplasia, features that mimic the pathophysiological changes observed in individuals with various forms of EE. We now test the hypothesis that adaptive T cell immunity is critical in initiating experimental EE. We first demonstrate that EE induction is associated with an increase in lymphocyte subpopulations (B+, CD4+, and CD8+ cells) in the esophagus. We induced experimental EE in wild‐type and various lymphocyte subpopulation‐deficient mice by intranasal allergen sensitization. Eosinophil levels and epithelial cell proliferation were determined by performing antimajor basic protein and antiproliferation cell nuclear antigen immunohistochemical analysis. Eosinophil accumulation in the esophagus was ablated completely in RAG1 gene‐deficient mice, but no role for B cells or antigen‐specific antibodies was found, as B cell‐deficient (IgH6) mice developed unabated, experimental EE. In addition, T cell‐deficient (forkhead box N1−/−) mice were protected from the induction of experimental EE. CD8α‐deficient mice developed unaltered, experimental EE, and CD4‐deficient mice were only protected moderately from disease induction. Taken together, these studies indicate a role for CD4+ and CD4− cell populations in EE pathogenesis and demonstrate that experimental allergen‐induced EE is dependent on adaptive T cell immunity.

Interleukin-15 Expression Is Increased in Human Eosinophilic Esophagitis and Mediates Pathogenesis in Mice

BACKGROUND & AIMS Quantitative microarray analyses have shown increased expression of interleukin-15 (IL-15) messenger RNA in the esophagus of patients with eosinophilic esophagitis (EoE), a recently recognized allergic disorder with poorly understood pathogenesis. METHODS Quantitative polymerase chain reaction and enzyme-linked immunosorbent assay analyses were performed to examine protein and transcript levels in tissue samples from patients with EoE. Tissues from IL-15Ra-deficient and wild-type (control) mice were also examined. Tissue eosinophilia was determined by immunostaining for major basic protein and flow cytometry for cell-surface receptors. RESULTS Quantitative polymerase chain reaction analyses showed that levels of IL-15 and its receptor IL-15Ra were increased approximately 6- and approximately 10-fold, respectively, in tissues from patients with EoE and approximately 3- and approximately 4-fold, respectively, in mice with allergen-induced EoE. A >2-fold increase in serum IL-15 protein levels was also detected in human EoE samples compared with those from healthy individuals. Human IL-15 messenger RNA levels correlated with esophageal eosinophilia (P < .001). IL-15Ra-deficient mice were protected from allergen-induced esophageal eosinophilia compared with controls (P < .001), even though similar levels of airway eosinophilia were observed in all mice. IL-15 activated STAT5 and CD4(+) T cells to produce cytokines that act on eosinophils. Incubation of primary esophageal epithelial cells from mice and humans with IL-15 caused a dose-dependent increase in the mRNA expression and protein levels of eotaxin-1, -2, and -3. CONCLUSIONS IL-15 mediates in the pathogenesis of EoE. IL-15 activates CD4(+) T cells to produce cytokines that act on eosinophils.

An imbalance of esophageal effector and regulatory T cell subsets in experimental eosinophilic esophagitis in mice

We recently reported a critical role for T cells in the induction of eosinophilic esophagitis (EE) in mice; however, the role of specific T cell subsets in disease pathogenesis is not yet understood. In the current study, we tested the hypothesis that allergen-induced EE develops in response to the disproportion of functionally different effector and regulatory T cells in the esophagus. Fluorescence-activated cell sorter analysis was performed to examine activated T cell subsets using the cell surface activation markers CD25 and CD69. A significant increase in activated CD4(+) and CD4(-) T cells was observed in the total esophageal cells isolated from the mouse model of EE. Furthermore, an imbalance in the effector and regulatory T cells was observed in the esophagus. The esophageal CD4(+)CD45RB(high) effector T cells in allergen-challenged mice increased compared with saline-challenged mice (65.4 +/- 3.6 x 10(3) to 44.8 +/- 4.2 x 10(3)), whereas CD4(+)CD45RB(low) mostly regulatory T cells decreased in allergen-challenged mice compared with saline-challenged mice (5.8 +/- 0.9 x 10(3) from 10.2 +/- 1.7 x 10(3)). The functional characteristics were examined by analysis of the pro- and anti-inflammatory cytokine profile of purified low and high CD4(+)CD45RB subsets from the spleen. Additionally, a significantly reduced interleukin (IL)-2 production by CD4(+)CD45RB(low) cells in allergen-challenged mice compared with saline-challenged mice was observed. The reduced IL-2 in the CD4(+)CD45RB(low) subset may be associated with reduction of CD4(+)CD45RB(low) subset. In conclusion, our results suggest that local regulatory interaction of CD45RB(high) and CD45RB(low) CD4(+) T cells may be required for protective and pathogenic immunity in EE.

Critical Role For Adaptive T Cell Immunity In Experimental Eosinophilic Esophagitis In Mice

We have previously developed a murine model of allergen-induced eosinophilic esophagitis (EE), characterized by intraepithelial eosinophils, extracellular granule deposition, and epithelial cell hyperplasia, features that mimic the pathophysiological changes observed in individuals with various forms of EE. We now test the hypothesis that adaptive T cell immunity is critical in initiating experimental EE. We first demonstrate that EE induction is associated with an increase in lymphocyte subpopulations (B+, CD4+, and CD8+ cells) in the esophagus. We induced experimental EE in wild-type and various lymphocyte subpopulation-deficient mice by intranasal allergen sensitization. Eosinophil levels and epithelial cell proliferation were determined by performing antimajor basic protein and antiproliferation cell nuclear antigen immunohistochemical analysis. Eosinophil accumulation in the esophagus was ablated completely in RAG1 gene-deficient mice, but no role for B cells or antigen-specific antibodies was found, as B cell-deficient (IgH6) mice developed unabated, experimental EE. In addition, T cell-deficient (forkhead box N1-/-) mice were protected from the induction of experimental EE. CD8alpha-deficient mice developed unaltered, experimental EE, and CD4-deficient mice were only protected moderately from disease induction. Taken together, these studies indicate a role for CD4+ and CD4- cell populations in EE pathogenesis and demonstrate that experimental allergen-induced EE is dependent on adaptive T cell immunity.