Each IgE antibody is specifically designed to bind to a particular substance, such as a specific type of foreign molecule. Foreign molecules include juniper pollen, penicillin , bee venom, and so on. IgE antibodies attach very tightly to cells with certain receptors. Some cells have many more of the specific receptors than others. One type of cells that circulates in the blood are called basophils.
Basophils are one of the body's tools for helping to fight infection.
Mast cells also have many receptors for IgE and are found in tissues throughout the body. When the IgE antibody binds to the basophil or mast cell receptors an IgE-cell complex is formed. When the IgE-cell complex binds to the foreign substance, the cell releases many biologically active substances, including histamine. In the body, after the antibody forms a cell complex, the cell complex looks for foreign bodies. Other antibodies can recognize foreign molecules and activate a special plasma defense mechanism called the complement system.