The monoclonal antibody BB7.2 specifically binds to the α subunit of the human leukocyte antigen-A2 (HLA-A2), a class I molecule of the major histocompatibility complex (MHC). The MHC gene locus encodes a group of highly polymorphic, cell-surface proteins that play a broad role in the immune response to protein antigens. MHC molecules bind and present small antigenic protein fragments to antigen-specific receptors expressed by T cells (TCR). Human (human leukocyte antigen/HLA) MHC molecules are comprised of two major classes, MHC class I and class II. Functionally, class I MHC molecules bind peptides derived from intracellular antigens (eg, viral and some bacterial antigens) which are specifically recognized by CD8+ T cells. Class II MHC molecules bind antigens derived from pathogens multiplying in intracellular vesicles and ingested extracellular bacteria, both of which are recognized by CD4+ T cells. TCR recognize processed peptides bound to the MHC as well as regions of the MHC molecule itself. CD4 and CD8 accessory molecules strengthen the formation of the TCR-MHC complex through their interaction with non-polymorphic regions of the MHC molecule.
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.