TLR4 and gastroesophageal reflux disease: Consistent with this information, this study further revealed a significant increase in the levels of the gut microbes Haemophilus and Klebsiella, which are involved in LPS synthesis in children with GERD, and Klebsiella is involved in LPS-mediated NF-κB activation and the production of inflammatory factors, such as TNF-α, IL-6 and IL-1β, through TLR4 (Sa-Pessoa et al., 2020).