The 2D7 monoclonal antibody selectively recognizes human basophils, Basophils (2D7). The antibody binds to a ~7.2 to 7.5 kDa basophil-specific protein, also known as the 2D7 antigen or ligand, present in secretory granules which has not been conclusively identified. Basophils normally comprise a relatively small percentage (<1%) of total peripheral blood leucocytes. Basophils express high levels of FceRI, a high affinity receptor for IgE. Upon activation through crosslinking of FceRI, basophils degranulate and may thus show reduced staining with the 2D7 antibody due to the release or destruction of the 2D7 antigen. The activated basophils release proinflammatory mediators that can either counter parasitic infections or lead to acute or chronic allergic diseases, including anaphylaxis, asthma, and atopic dermatitis. Activated basophils release a variety of mediators including the vasodilator histamine, proteolytic enzymes, and several cytokines which promote inflammation as well as heparin which prevents blood clotting. The 2D7 monoclonal antibody is useful for identifying human basophils since it does not recognize lymphocytes, monocytes, eosinophils, neutrophils, or mast cells.