Immunoglobulin E (IgE) antibodies are synthesized and secreted into the blood and tissues by B cells, and the regulation of their production and secretion is mediated by T cells. When specific allergens, such as pollen, mold, and dust mites, enter the body, the body's immune system stimulates T cells to produce and secrete the cytokines IL-4 and IL-13. These cytokines then stimulate B cells to differentiate into IgE-secreting cells, which produce and secrete large amounts of IgE antibodies that bind to the surface receptor on cells called FcεR, resulting in the formation of IgE/FcεR complexes. These complexes circulate in the body and deposit on the surface of tissue cells, such as mast cells and eosinophils.