The SK3 monoclonal antibody specifically binds to CD4. The CD4 antigen is a 55 kDa type 1 transmembrane glycoprotein that belongs to the immunoglobulin superfamily. It is expressed on T-helper/inducer lymphocytes and monocytes. CD3+CD4+ T cells comprise approximately 28% to 58% of normal peripheral blood lymphocytes. CD4 is also expressed on 80% to 95% of normal thymocytes. The CD4 antigen is present in low density on the cell surface of monocytes and in the cytoplasm of monocytes and macrophages (CD3-CD4+). CD4 serves as a T cell coreceptor for MHC class II antigen recognition and as a receptor for the human immunodeficiency virus (HIV). The SK3 antibody inhibits HIV binding to CD4+ cells.
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.
