CD45RA is an isoform of the CD45 complex and has restricted expression between different subtypes of lymphoid cells. CD45 (LCA, leukocyte common antigen) is a receptor-type protein tyrosine phosphatase ubiquitously expressed in all nucleated hematopoietic cells, comprising approximately 10% of all surface proteins in lymphocytes. CD45 glycoprotein is crucial in lymphocyte development and antigen signaling, serving as an important regulator of Src-family kinases. CD45 protein exists as multiple isoforms as a result of alternative splicing and these isoforms differ in their extracellular domains, however, they share identical transmembrane and cytoplasmic domains. CD45 isoforms differ in their ability to translocate into the glycosphingolipid-enriched membrane domains and their expression depends on cell type and physiological state of the cell. Besides the role in immunoreceptor signaling, CD45 is important in promoting cell survival by modulating integrin-mediated signal transduction pathway and is also involved in DNA fragmentation during apoptosis. CD45 is expressed on cells of the human hematopoietic lineage, with the exception of mature red cells and is not detected on differentiated cells of other tissues. It is likely that CD45 plays an important role in signal transduction, inhibition or upregulation of various immunological functions. Diseases associated with CD45 dysfunction include severe combined immunodeficiency and Hepatitis C.
CD45; CD45 antigen; L-CA; Leukocyte common antigen; Lyt-4; protein tyrosine phosphatase, receptor type, C; protein tyrosine phosphatase, receptor type, c polypeptide; Receptor-type tyrosine-protein phosphatase C; T100; T200; T200 glycoprotein; T200 leukocyte common antigen