Leukocyte common antigen (CD45) (CD45)

Leukocyte common antigen, widely known as CD45, is a high-molecular-weight transmembrane glycoprotein expressed on the surface of all hematopoietic cells except mature erythrocytes and platelets. It functions as a receptor-type protein tyrosine phosphatase (PTPase) and plays a critical role in regulating T-cell and B-cell antigen receptor signaling by dephosphorylating members of the Src family kinases, such as Lck and Fyn. CD45 exists in multiple isoforms (ranging from 180 to 220 kDa) generated by alternative splicing of exons 4, 5, and 6 (A, B, and C), with the 190 kDa variant often associated with specific T-cell subsets or activation states. In clinical medicine, CD45 is a primary marker for identifying hematolymphoid neoplasms and is a target for therapeutic interventions, including radioimmunotherapy and hematopoietic stem cell transplantation conditioning. Its essential role in lymphocyte activation makes it a key molecule for understanding immune system regulation and developing treatments for autoimmune diseases and cancers.

Other names

CD45Leukocyte common antigenLCAT200GP180LY5Protein tyrosine phosphatase receptor type CPTPRCSialophorin (sometimes confused in older literature)B220 (mouse isoform)

Targeted cell depletion via radioimmunotherapy, inhibition of phosphatase activity, modulation of T-cell receptor signaling threshold