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.
The antibody was conjugated to BD Horizon BB700, which is part of the BD Horizon Brilliant™ Blue family of dyes. It is a polymer-based tandem dye developed exclusively by BD Biosciences. With an excitation max of 485 nm and an emission max of 693 nm, BD Horizon BB700 can be excited by the 488 nm laser and detected in a standard PerCP-Cy™5.5 set (eg, 695/40-nm filter). This dye provides a much brighter alternative to PerCP-Cy5.5 with less cross laser excitation off the 405 nm and 355 nm lasers.