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.
This antibody is conjugated to BD Horizon™ BV605 which is part of the BD Horizon Brilliant™ Violet family of dyes. With an Ex Max of 407-nm and Em Max of 602-nm, BD Horizon BV605 can be excited by a violet laser and detected with a standard 610/20-nm filter set. BD Horizon BV605 is a tandem fluorochrome of BD Horizon BV421 and an acceptor dye with an Em max at 605-nm. Due to the excitation of the acceptor dye by the green (532 nm) and yellow-green (561 nm) lasers, there will be significant spillover into the PE and BD Horizon PE-CF594 detectors off the green or yellow-green lasers. BD Horizon BV605 conjugates are very bright, often exhibiting brightness equivalent to PE conjugates and can be used as a third color off of the violet laser.