Rosenberg CE, et al. - Given recent data associate eosinophilic esophagitis (EoE) with IgG4 rather than IgE, researchers performed this case-control study involving pediatric subjects with EoE (≥15 eosinophils/HPF) and non-EoE controls to measure esophageal IgG4 levels and to determine functional correlations as assessed by histologic and transcriptome analyses. Findings portrayed IgG4 as a relevant feature of the disease. Furthermore, a close relation of IgG4 to esophageal eosinophil levels, type 2 immunity and T regulatory cytokines was observed. Local production of IgG4 was speculated. As an extension of prior studies on IgG4 in adult EoE to the pediatric population, this study offered an in-depth insight into the potential significance and regulation of IgG4.