Specificity: Recognizes the human high affinity Fc receptor for IgE (Fc epsilon R1), which plays a central role in the IgE-mediated allergic response. Fc epsilon R1 consists of four subunits, a high affinity IgE binding alpha subunit, a beta chain and two disulfide linked gamma subunits. Clone Recognizes the extracellular D1 domain of the Fc epsilon R1 alpha chain. Fc epsilon R1 is primarily expressed on mast cells and basophils but expression of Fc epsilon R1 has also been reported on monocytes, Langerhans cells and dendritic cells from patients with atopic diseases