Erythrocytes and platelet adhesion to endothelium are mediated by specialized molecules

Erythrocytes in normal conditions have weak interactions with other blood cells and endothelial cells while in pathological circumstances they can adhere to endothelium and aggregate or agglutinate to blood cells. Erythrocyte adhesion was found to be abnormal in sickle cell anemia and diabetes mellitus and correlated to the vascular complications. Further studies demonstrated that VLA-4 adhesion molecule (alpha4beta1) present on erythrocytes bound to vascular cell adhesion molecule (VCAM-1) of the endothelium. In addition, the blood group Lutheran molecule (LU) overexpressed on sickle erythrocytes bind to laminin present on cells or in the intercellular space. In diabetes mellitus the formation of advanced glycation end products (AGE) by reaction between carbohydrates and free aminogroups of lysine is responsible for red blood cell membrane glycation. AGEs present on RBCs bind to the receptor for AGE (RAGE) on endothelium, activating endothelial cells. A molecule related to blood group Rhesus was demonstrated to belong to the intercellular adhesion molecule (ICAM) family. ICAM-4 binds to integrins present on leukocytes (CD11-CD18) and on platelets (alpha2beta4) offering a surface, which can be involved in thrombosis. The identification of erythrocytes adhesion molecules open a new way to understand thrombotic processes and vascular dysfunction.