CD4 and eosinophilic esophagitis: With the aim of exploring non-invasive biomarkers, the studies done in peripheral blood mononuclear cells (PBMCs) in active EoE patients demonstrated an increase in circulating CD4+/CD8+ Tcell ratio (24), and the alteration of activation markers in specific populations of immune cells after their contact with the affected esophageal mucosa (26).