The HIS57 monoclonal antibody reacts with an unknown antigen that is highly expressed by most marginal zone B (MZ-B) cells in the spleen. In contrast, this antigen is weakly expressed, or not expressed at all, by other B-cell subpopulations. Rat MZ-B cells express low levels of CD45R (mAb HIS24) and sIgD and high levels of sIgM. The HIS57 mAb does not stain granulocytes and thymocytes. Immunohistochemical staining of normal spleen sections with HIS57 mAb produced a positive signal in the marginal zone and, to a lesser extent, in B-cell follicles. This marker can be used in combination with CD45R, sIgD, and sIgM t0 identify MZ-B cells in the rat.
The antibody was conjugated to BD Horizon™ BUV661 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 with an Ex Max of 348-nm and an acceptor dye with an Em Max at 661-nm. BD Horizon Brilliant BUV661 can be excited by the ultraviolet laser (355 nm) and detected with a 670/25 filter and a 630 nm LP. Due to cross laser excitation of this dye, there may be significant spillover into channels detecting APC-like emissions (eg, 670/25-nm filter).
Due to spectral differences between labeled cells and beads, using BD™ CompBeads can result in incorrect spillover values when used with BD Horizon BUV661 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV661 reagents (eg, CD4 vs. CD45) can have slightly different fluorescence spillover therefore, it may also be necessary to use clone-specific compensation controls when using these reagents.