TLR4 and gastroesophageal reflux disease: TLR4 expression is increased in patients with GERD, triggering an inflammatory response involved in the further development of GERD.TLR4 expression in normal squamous epithelial samples is mainly confined to the basal layer of the squamous epithelium, which routinely may not come into contact with PAMPs expressed by the esophageal microbiota, and reflux increases TLR4 expression (49).