The MAR-1 monoclonal antibody specifically recognizes Fc-epsilon RI-alpha (FceR1 alpha, also known as FcεR1α or FcER1a) which is likewise known as the IgE Fc receptor subunit alpha. FcεR1α is a type I transmembrane glycoprotein that is encoded by Fcer1a (Fc receptor, IgE, high affinity I, alpha polypeptide) which belongs to the Ig gene superfamily. As a single IgE-binding alpha subunit, FcεR1α complexes with signal transducing subunits including one beta subunit (FcεRIβ encoded by Ms4a2) and two disulfide-linked gamma subunits (FcεRIγ encoded by Fcer1g) to form the high-affinity receptor for IgE, Fc epsilon RI (FcεR1 or FcER1). FcεR1 is expressed on basophils and mast cells. Binding of cognate antigens (allergens) to FcεR1 with bound IgE antibodies leads to cellular activation and the release of mediators, including histamine and cytokines, that are responsible for allergic reactions. Tang et al. (2019) have reported that the MAR-1 antibody crossreacts with two other mouse Fc receptor chains, FcγRI (CD64) and FcγRIV (CD16-2), that are expressed by monocytes, macrophages, dendritic cells, or neutrophils. They suggested MAR-1 binding is specific for FcεRIa only on mast cells and basophils and that for other cell types reactive with the MAR-1 antibody, it may be appropriate to refer to these as MAR-1-positive (MAR-1+) cells.
The antibody was conjugated to BD Horizon™ BUV395 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye has been exclusively developed by BD Biosciences to have minimal spillover into other detectors, making it an optimal choice for multicolor flow cytometry. With an Ex Max at 348 nm and an Em Max at 395 nm, BD Horizon BUV395 can be excited with a 355 nm laser and detected with a 379/28 filter.