The 8G12 monoclonal antibody specifically recognizes CD34, a 105-120 kDa single-chain type I transmembrane glycoprotein. The 8G12 antibody recognizes an epitope on CD34 distinct from the one recognized by clone My10. CD34 is expressed on immature hematopoietic precursor cells and all hematopoietic colony-forming cells in bone marrow and blood, including unipotent (CFU-GM, BFU-E) and pluripotent progenitors (CFU-GEMM, CFU-Mix, and CFUBlast). The CD34 antigen is a differentiation stage-specific leucocyte antigen. Terminal deoxynucleotidyl transferase-positive B- and T-lymphoid precursors in normal bone marrow are CD34+. The CD34 antigen is present on early myeloid cells that express the CD33 antigen but lack the CD14 and CD15 antigens and on early erythroid cells that express the CD71 antigen and dimly express the CD45 antigen. The CD34 antigen is also found on capillary endothelial cells and approximately 1% of human thymocytes. Normal peripheral blood lymphocytes, monocytes, granulocytes, and platelets do not express CD34. CD34 density is highest on early hematopoietic progenitor cells and decreases as cells mature. The antigen is absent on fully differentiated hematopoietic cells. Uncommitted CD34+ progenitor cells are CD38- and lack lineage-specific antigens such as CD71, CD33, CD10, and CD5, while CD34+ cells that are lineage-committed express the CD38 antigen in high density. Most CD34+ cells reciprocally express either the CD45RO or CD45RA antigens, with the CD45RO+ population being the more primitive. Approximately 60% of acute B-lymphoid leukemias and acute myeloid leukemias (AML) and 1% to 5% of acute T-lymphoid leukemias express CD34. CD34 is not expressed on chronic lymphoid leukemias or lymphomas.
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.