Protein tyrosine phosphatase receptor type C isoform B (CD45RB)

Protein tyrosine phosphatase receptor type C isoform B (CD45RB) is a high-molecular-weight transmembrane glycoprotein and a key member of the protein tyrosine phosphatase (PTP) family (UniProt P08575). It is an alternatively spliced variant of the PTPRC gene, characterized by the inclusion of exon 5 (exon B), and is predominantly expressed on the surface of various hematopoietic cells, including naive and certain effector T cells, B cells, and monocytes (NCBI Gene 5788). CD45RB functions as a critical regulator of immune cell signaling by dephosphorylating the inhibitory C-terminal tyrosine residue of Src-family kinases, such as Lck and Fyn, which is essential for initiating T-cell and B-cell receptor-mediated activation (PubMed 35767951). In therapeutic contexts, CD45 is a prominent target for radioimmunotherapy, such as Apamistamab (Iomab-B), which delivers targeted radiation to leukemic cells as a conditioning regimen for bone marrow transplantation (J Clin Oncol 2024). Furthermore, CD45RB expression serves as a biomarker for naive T-cell populations and has been extensively investigated as a target for inducing immune tolerance in organ transplantation and managing autoimmune diseases like inflammatory bowel disease.

Other names

CD45RBPTPRC isoform BLeukocyte common antigen isoform BLCA isoform BT200 isoform BLy-5 isoform BProtein tyrosine phosphatase receptor type C isoform 2

CD45RB regulates immune signaling by dephosphorylating the inhibitory C-terminal tyrosine of Src-family kinases (SFKs), thereby enabling kinase activation and downstream signaling from antigen receptors; targeted therapies like Apamistamab use anti-CD45 antibodies to deliver cytotoxic radioisotopes to hematopoietic and leukemic cells.