The S5.2 monoclonal antibody specifically recognizes the CD2 antigen, a 45 to 50 kDa type I transmembrane glycoprotein that forms the binding site for sheep erythrocytes. The CD2 antigen is present on approximately 75% of normal peripheral blood lymphocytes and 95% to 99% of thymocytes. It is also found on a subset of monocytes (approximately one-third) that might be precursors to dendritic cells. The CD2 antibody reacts with essentially all T lymphocytes and with a subset of NK lymphocytes. CD2 and CD58 have been shown to be coreceptors. The interaction of CD2 antigen and CD58 antigen facilitates antigen recognition by T lymphocytes.
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.