CD45. also known as leukocyte common antigen (LCA), is a transmembrane protein tyrosine phosphatase expressed on all nucleated hematopoietic cells, including lymphocytes, monocytes, granulocytes, and dendritic cells. Discovered in the 1970s, CD45 plays a critical role in regulating immune cell activation by modulating signaling through antigen receptors. Its extracellular domain exhibits alternative splicing, generating isoforms (e.g., CD45RA, CD45RO) that serve as markers for cell differentiation and activation states. CD45 antibodies, developed against specific epitopes of these isoforms, have become indispensable tools in immunology research and clinical diagnostics.
In research, CD45 antibodies are widely used in flow cytometry to identify and isolate leukocyte subsets. They also aid in studying T-cell receptor (TCR) and B-cell receptor (BCR) signaling pathways, as CD45 dephosphorylates inhibitory tyrosine residues on Src-family kinases, enabling receptor activation. Clinically, CD45 antibodies are employed in immunohistochemistry to distinguish hematopoietic malignancies (e.g., leukemia, lymphoma) from non-hematopoietic tumors. Additionally, CD45 targeting has therapeutic potential; antibody-drug conjugates or radioimmunotherapy agents are being explored to selectively eliminate malignant immune cells.
Despite its broad utility, CD45’s role in immune regulation remains complex. Its isoforms exhibit context-dependent functions in autoimmunity, infection, and transplantation tolerance. Ongoing studies aim to unravel isoform-specific mechanisms and refine CD45-targeted therapies. Overall, CD45 antibodies continue to bridge foundational immunology with translational applications in disease diagnosis and treatment.