Lymphocyte–Endothelial Interactions

The vascular and lymphatic endothelia are monolayers of cells that line the cardiovascular and lymphatic systems, respectively. These serve as the critical partition between the tissues and the contiguous blood-lymph compartments. Thus, the endothelium is strategically positioned to serve as a unique sentinel for communicating interstitial information to circulating immune cells. In this way, the endothelium plays critical roles not only in directing the trafficking patterns of immune cells, but also in determining their functional states. In particular the endothelium has emerged as unique peripheral major histocompatibility complex – and co-stimulatory/co-inhibitory molecule – expressing ‘semi-professional’ antigen presenting cell (APC). Intimate dynamic probing of these APCs by trafficking T lymphocytes via invadosome-like protrusions provides a basis for antigen recognition in this setting that can contribute distinctly to adaptive immune regulation.