Roles of systemic CD4

Large-animal models are valuable for investigating the pathogenesis, natural history and therapeutic responses of eosinophilic esophagitis (EoE). We previously developed a porcine EoE model using hen egg white protein (HEWP) sensitization and oral challenge, but additional immunophenotyping is needed - particularly of esophageal mast cells (MC) and systemic CD4 T-cell responses. This study evaluated whether the model induces MC infiltration into the esophagus and whether systemic allergen-specific CD4 T cells correlate with esophageal eosinophilia. Pigs underwent three weekly intraperitoneal sensitizations with HEWP plus cholera toxin followed by one week of daily oral HEWP. Controls included: mock (n=3); sensitization only (n=3); and challenge only (n=3). For EoE induction, nine animals received both sensitization and challenge. MCs were identified by tryptase immunohistochemistry and peak MC counts per high power field (hpf) were manually quantified in the epithelium, lamina propria and muscularis. Systemic HEWP (ovalbumin, OVA)- specific CD4 T cells were quantified via flow cytometry and eosinophilic infiltration was determined by H&E staining. Correlations were analyzed using Spearman's test. Sensitized and challenged pigs exhibited significantly elevated MC infiltration across all esophageal layers compared to controls. MC increases were mild in the epithelium (4.4 ±3.5 MCs/hpf vs 1.7 ±2.4; p=0.0064) but pronounced in the lamina propria (17.9 ±7.8 vs 9.1 ±7.2; p=0.0001) and muscularis (17.2 ±8.0 vs 12.1 ±11.8; p=0.0002). Moreover, systemic OVA-specific CD4 T-cell frequency positively correlated with esophageal eosinophil counts (R2=0.51; p=0.001). These findings support that our EoE model recapitulates the pathogenesis of human EoE as a type-2 inflammatory disease with multicellular infiltrate of eosinophils and MCs.