The MAR-1 antibody reacts with the Fc epsilon Receptor I alpha chain (FceRIa), a transmembrane protein member of the Ig superfamily. This chain, together with a beta chain and two gamma chains form a tetrameric complex that supports IgE-mediated signaling and subsequent release of chemical mediators of allergy and immediate hypersensitivity. FceR1a is upregulated in the presence of IgE on those cell types which express it, such as Mast cells and Basophils.The MAR-1 antibody is widely used both in flow cytometry and for depletion of cells in vitro / in vivo.