Endothelial cells lining the microvasculature play a critical “gatekeeper” role in the inflammatory process through their ability to recruit circulating immune cells into tissues and foci of inflammation. Human Esophageal Microvascular Endothelial Cells (HEsMEC) exhibit a strong inflammatory immune response to LPS, cytokines, and pH exposure, thus playing a critical regulatory role in esophageal inflammation. When exposed to acidic pH, HEsMEC express certain proteins, such as VCAM-1, but not others, such as ICAM-1. This expression pattern could play a role in the cellular response triggered by gastroesophageal reflux disease. HEsMEC cultures have enabled scientists to observe leukocyte binding, upregulation of cell adhesion molecules, and other cellular responses to LPS, cytokines and pH exposure. HEsMEC are intrinsically different from lower gastrointestinal endothelial cells.