The mAb I3/2.3 recognizes mouse CD45, which is also known as the leukocyte common antigen (L-CA or LCA), T200, or Lymphocyte antigen 5 (Ly-5). CD45 is a 180-240 kDa single-pass type I transmembrane glycoprotein that is encoded by Ptprc (protein tyrosine phosphatase, receptor type, C) which belongs to the protein tyrosine phosphatase (PTP) family. CD45 is variably expressed on thymocytes and other hematopoietic cells except mature erythrocytes and platelets. Different isoforms of CD45 arise from alternative splicing of variable exons 4, 5, and 6, which encode A, B, and C determinants, respectively, that encode extracellular domains of the transmembrane receptor. The differential expression of these isoforms is related to the cell's lineage as well as its state of activation and maturation. The mAb I3/2.3 reportedly recognizes all CD45 isoforms. CD45 plays key roles as a protein tyrosine-protein phosphatase in leucocyte responses including signal pathways transduced by antigen specific receptors expressed on T cells (TCRs) and B cells (BCRs).
The antibody was conjugated to BD Horizon™ BUV563 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 which has an Ex Max of 348 nm and an acceptor dye. The tandem has an Em Max at 563 nm. BD Horizon BUV563 can be excited by the 355 nm ultraviolet laser. On instruments with a 561 nm Yellow-Green laser, the recommended bandpass filter is 585/15 nm with a 535 nm long pass to minimize laser light leakage. When BD Horizon BUV563 is used with an instrument that does not have a 561 nm laser, a 560/40 nm filter with a 535 nm long pass may be more optimal. Due to the excitation and emission characteristics of the acceptor dye, there may be spillover into the PE and PE-CF594 detectors. However, the spillover can be corrected through compensation as with any other dye combination.