Endothelial Cells: Immunological Aspects

Abstract

Strategically located at the interface between blood and the extravascular space, the endothelium is a highly specialised cellular system, which plays a key role in physiological processes such as blood supply, nutrient delivery, metabolic homeostasis and immune cell trafficking, as well as pathological processes such as inflammation. Endothelial cells represent a highly heterogeneous population of cells with the ability to interact with and modulate the function of immune cells. These cells regulate the traffic and functions of leucocytes by expressing adhesion molecules and cytokines in a regulated way. The ability of endothelial cells to compartmentalise memory T‐cell responses via organ‐selective expression of homing receptor ligands and to recruit antigen‐specific T cells into inflammatory sites by displaying cognate major histocompatibility complex–peptide complexes contributes a new dimension to the central role played by endothelium in the regulation of immune responses. Key Concepts Endothelial cells are not just an inert barrier between the blood and parenchyma. The endothelial cell orchestrates cellular processes key to the inflammatory reaction. A regulated use of different adhesion molecules and chemokines guides tissue‐specific leucocyte extravasation. Especially, microvascular endothelial cells can act as antigen‐presenting cells, leading to T lymphocyte extravasation. Endothelial cells are both targets for and a source of cytokines – soluble polypeptides acting as mediators of communication with leucocytes and other cells. Vasculature senescence plays an active role in promoting an inflammatory response.