MT4 (6B6) reacts with the 190, 205 and 220 kDa isoforms of the glycoprotein cell-surface antigen, CD45RB. The antigen is expressed primarily on a subset of human B and T lymphocytes, monocytes, macrophages and granulocytes (weak). CD4+, CD45RA- (memory T cells) cells show a differential expression of CD45RB. Bright CD45RB expression correlates with higher proliferation and IFNγ production when compared with dim CD45RB expression. CD45RB expression may be a mechanism for fine-tuning the responsiveness of memory cells in vivo.
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.