Chemokine receptors & associated diseases (Proudfoot, A., Nature Rev Immunol. 2002) Step 1: CaptureEndothelial cells that are exposed to cytokines, primarily on their basal side (away from the blood), once activated, will express adhesion molecules on their apical or luminal side. The main adhesion molecule expressed by endothelial cells which is used for leukocyte capture is P-selectin. P-selectin is the largest member of the selectin family of transmembrane molecules. Selectins contain a lectin domain, an epidermal growth factor (EGF) domain, 2-9 consensus repeats (CR), a transmembrane domain and a short cytoplasmic tail. P-selectin is the longest of the lectins with 9 consensus repeats, E-selectin has 6 repeats and L-selectin is the shortest with only 2 repeats. While P-selectin is expressed by inflamed endothelium and platelets, L-selectin is found on most leukocytes and E-selectin is found on inflamed endothelium. All selectins require calcium present in their lectin domain to bind their receptors.