Cytokeratins (CK) are intermediate filaments of epithelial cells, both in keratinising tissue (ie., skin) and non keratinising cells (ie., mesothelial cells). Although not a traditional marker for endothelial cells, cytokeratins have also been found in some microvascular endothelial cells. At least 20 different cytokeratins (CK) in the molecular range of 40 to 70 kDa and isoelectric points of 5 to 8.5 can be identified using two dimensional gel electrophoresis. Biochemically, most members of