Surface markers

Definition

Surface markers are specific proteins found on the surface of the cell which can be used for its identification. They can play different roles in the cell (e.g. function as either receptors or ligands); they are classified as markers exclusively based on their specificity for a particular type of cell. Cluster of differentiation (CD) is a system of surface molecule identification used for so-called immunophenotyping of the cells. For each type of cell, there is a specific combination of known CD antigens. For example, the markers specific to mesenchymal stem cells (MSC) are CD73 (5’-nucleotidase), CD90 (Thy-1) and CD105 (endoglin); apart from that, they also typically express CD29 (integrin beta-1), CD44, and CD106 (VCAM-1) markers, and lack of CD34 and CD45, the markers specific for hematopoietic cells.