{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"The CD45 family consists of multiple members that are all products of a single complex gene. CD45 was originally called Leukocyte Common Antigen. It is a Type I transmembrane protein which is in various isoforms present on all differentiated hematopoietic cells except erythrocytes and assists in the activation of those cells (a form of co-stimulation). Three isoforms of CD45 exist: on B-lymphocytes, where the protein is called B220 (its molecular mass is 220 kDA); on naive T-lymphocytes, where it is called CD45 RA, and on activated and memory T-lymphocytes, where it is called CD45 RO. Detection of the different isoforms can distinguish between different cell forms (e.g., naive T-cells and memory T-cells).\nCD45RO, a single-chain, transmembraneous glycoprotein, represents the low molecular weight isoform of the Leukocyte Common Antigen (LCA). It is expressed on most thymocytes, about 45% of peripheral blood T-cells, virtually all T-cells in skin reactive infiltrates, and the majority of T-cell malignancies. It is also found on a subset of B-cells and on exceptional B-cell Lymphomas"}]}]}