The B7/21 monoclonal antibody specifically recognizes HLA-DP antigens which are human Major Histocompatibility Complex (MHC) Class II antigens. HLA-DP antigens are heterodimers comprised of two different type I transmembrane glycoproteins that are noncovalently-associated. The ~34 kDa HLA-DP alpha (HLA-DPα) and ~26-28 kDa HLA-DP beta (HLA-DPβ) chains are encoded by HLA-DPA1 and HLA-DPB1 genes, respectively, that are located within the Human Leukocyte Antigen (HLA) Complex of chromosome 6. The B7/21 antibody recognizes a monomorphic determinant present on cells expressing HLA-DP1, -DP2, -DP3, -DP4, and -DP5 and does not reportedly bind to HLA-DR or HLA-DQ Class II antigens. HLA-DP is variably expressed on B cells, monocytes, macrophages, dendritic cells (DC), activated T cells, and tumor cell lines including B cell lines, myelomas, and some myeloid leukemias. HLA-DP functions in the presentation of peptides derived from extracellular antigens to CD4+ T cells.
The original B7/21 hybridoma was derived from hybridization of mouse 5194/SXXOBU1 myeloma cells with spleen cells from BALB/c mice immunized with NALM6 human leukemia cells and secreted IgG3, κ antibody. An immunoglobulin switch-variant B7/21 hybridoma, also known as B7/21.49 or B7/21 (IgG1), was subsequently isolated that secreted lgG1 antibody with the same specificity as the original IgG3 antibody. The purified switch-variant B7/21 IgG1 antibody blocks the staining of HLA-DP-positive cells by fluorescent B7/21 IgG3 antibody. The B7/21 IgG1 antibody is reportedly not cytotoxic in the presence of complement.
This antibody is conjugated to BD Horizon™ BV605 which is part of the BD Horizon Brilliant™ Violet family of dyes. With an Ex Max of 407-nm and Em Max of 602-nm, BD Horizon BV605 can be excited by a violet laser and detected with a standard 610/20-nm filter set. BD Horizon BV605 is a tandem fluorochrome of BD Horizon BV421 and an acceptor dye with an Em max at 605-nm. Due to the excitation of the acceptor dye by the green (532 nm) and yellow-green (561 nm) lasers, there will be significant spillover into the PE and BD Horizon PE-CF594 detectors off the green or yellow-green lasers. BD Horizon BV605 conjugates are very bright, often exhibiting brightness equivalent to PE conjugates and can be used as a third color off of the violet laser.