(A and B) WT and DR3.DQ2 mice were fed control (gluten-free) or gluten-enriched diets for 14 days prior to oral HB-230 administration (10 mg/kg). Two hours later, tissues were collected and stained. (A) DR3.DQ2 mice on a gluten-enhanced diet showed increased HB-230 labeling at villus tips. Dot plot quantifies extracellular HB-230⁺ villi per 10 villi. (B) Confocal imaging revealed strong colocalization of HB-230 with TG2 at villus tips, indicating increased ECM-associated TG2 activity. P values were determined using a 2-way ANOVA, and multiple comparisons were assessed using Benjamini, Krieger, and Yekutieli’s 2-stage step-up method. *P < 0.05. Data represent mean ± SEM. (C–E) DdVil-IL15 transgenic and WT mice received HB-230 (10 mg/kg), and intestines were collected 2 hours later. (C) Quantification of HB-230⁺ signal (pixel area relative to total tissue area) in proximal and distal intestine sections revealed increased TG2 activity in DdVil-IL15 mice. (D) Flow cytometry of lamina propria cells showed a higher frequency of CD11c⁺ DCs, but not CD19⁺ B cells or F4/80⁺ macrophages, among total HB-230⁺CD45⁺MHCII⁺ cells in DdVil-IL15 mice. (E) Representative flow cytometry plots of HB-230⁺CD103⁺ DCs in WT (n = 8) vs. DdVil-IL15 (n = 5) mice. P values were determined using a 2-way ANOVA, and multiple comparisons were assessed using Benjamini, Krieger, and Yekutieli’s 2-stage step-up method. *P < 0.05. Data shown as mean ± SEM. (F) WT mice were infected with T1L reovirus or treated with PBS 46 hours prior to HB-230 administration. Confocal images showed increased extracellular HB-230 staining in distal intestines of reovirus-infected WT mice. P values were determined using a 2-way ANOVA, and multiple comparisons were assessed using Benjamini, Krieger, and Yekutieli’s 2-stage step-up method. *P < 0.05. Data shown as mean ± SEM.