sentinel cell sentinel cell sentinel cells refer to cells in the body's first line of defense, which embed themselves in tissues such as skin. sentinel cells can refer to specific antigen-presenting cells, such as: macrophages kupffer cells - in the liver langerhans cells - in the skin and mucosa (*these are a form of dendritic cells) alveolar macrophages - in the lungs microglia - in the brain dendritic cells sentinel cells can also refer to cells that are normally not specialized antigen-presenting cells such as: mast cells specialized t cells sometimes tissue cells not part of the immune system such as are also referred to as sentinel cells: fibroblasts epithelial cells