IMMUNOLOGY

Detailed explanation-1: -There are two IgE receptors: FcRI is the high-affinity IgE receptor that is expressed by mast cells and basophils and by dendritic cells and Langerhans cells in the skin.

Detailed explanation-2: -Allergic reactions are triggered when allergens cross-link preformed IgE bound to the high-affinity receptor FcRI on mast cells. Mast cells line the body surfaces and serve to alert the immune system to local infection.

Detailed explanation-3: -Mast cells are tissue resident cells and uniquely required for immediate hypersensitivity. Basophils are largely circulating cells, but home to areas of allergic inflammation during the late phase response. Eosinophils are resident to the GI tract, but also home to allergic inflammatory sites.