PROS1 and eosinophilic esophagitis: Previous studies that profiled the EoE proteome aimed to characterize extracellular matrix proteins secreted by fibroblasts (20), focused on cysteinyl-S-nitrosylated proteins in the esophageal biopsies (39), or developed a highly sensitive, antibody-like peptide–targeting method for detecting eosinophilic cationic protein in the mucus of patients with active EoE (40).