CD45 is a type I transmembrane glycoprotein that is encoded by the PTPRC gene in humans and is abundantly expressed on nucleated hematopoietic cells. It contains an extracellular region that binds to glycoproteins and exists in various isoforms in a cell type-, differentiation state-, and activation state-dependent manner. CD45 also contains two highly conserved cytoplasmic protein tyrosine phosphatase domains that regulate intracellular signaling. CD45 functions as a negative or positive regulator of antigen receptor signaling in T and B cells through dephosphorylation of Src family kinases in a cell type- and differentiation state-dependent manner. It also dephosphorylates JAK kinases, inhibiting cytokine and chemokine signaling in leukocytes. Mutations in PTPRC are associated with severe combined immunodeficiency (SCID) in mice and humans. The number of CD45+ cells is increased in postmortem brain from patients with Alzheimer''s disease. Increased levels of the CD45 isoform CD45RO have been found on CD19+ lamina propria B cells isolated from patients with Crohn''s disease. Fluorescently labeled versions of CD45 have commonly been used in flow cytometry as a pan leukocyte marker and to identify certain subsets of hematopoietic stem cells (HSCs). Cayman''s CD45 Monoclonal Antibody (Clone BRA-55) can be used for flow cytometry (FC), immunocytochemistry (ICC), immunohistochemistry (IHC), and Western blot (WB) applications. The antibody recognizes CD45 at approximately 170 to 220 kDa from human samples.
