mastocyte

CONT: Those mast cells, relatives of white blood cells, are common in the surface tissues of the body, where they wait for reexposure to the antigen like mines floating in a harbor. When the antigen returns and touches two or more IgE molecules, the mast cell pours out a cocktail of at least ten chemicals. Some are enzymes that attack any nearby cells; some activate platelets; some attract other white cells to the site; some can stimulate smooth muscle (thereby causing asthma). One, histamine, causes itching and swelling, unpleasant effects that can be blocked by antihistamines.