Background：CD45 is a 180-240 kD glycoprotein also known as the leukocyte common antigen （LCA）, T200, or Ly-5. It is a member of the protein tyrosine phosphatase （PTP） family, expressed on all hematopoietic cells except mature erythrocytes and platelets. There are different isoforms of CD45 that arise from alternative splicing of exons 4, 5, and 6, which encode A, B, and C determinants, respectively. CD45 plays a key role in TCR and BCR signal transduction. These isoforms are very specific to the activation and maturation state of the cell as well as cell type. The primary ligands for CD45 are galectin-1, CD2, CD3, CD4, TCR, CD22, and Thy-1.
