The main limitation of our study is the presence of selection bias in the GERD patient group, as these patients present with acid reflux and higher PPI use, which prevents certain lymphocyte populations (CD45+CD3− cells, ILC, CD4+ and CD8+ in the lamina propria and NKT and ILC3 at the intraepithelial level) from being used as a “gold standard” since significant differences were observed between the GERD group and healthy controls. This evidence concerns the gene CCL27 and gastroesophageal reflux disease.