Mast cells contain metachromatic granules which store a variety of inflammatory mediators. They are generally classified as connective tissue and mucosal mast cells. Their origin and kinetics are poorly understood. The major inflammatory function of mast cells is the release of vasoactive amines in the very early stages of an inflammatory process. Products of arachidonate metabolism and platelet activating factor are also important mast cell products that function as inflammatory mediators.
Mast cells are important mediators of certain allergic reactions.
Mast cell membranes have abundant IgE receptor sites, anywhere from 30,000 to 500,000 per cell. If a particular antigen incites an IgE response, the resulting IgE is bound to the IgE receptors on mast cell surfaces via the Fc portion of the immunoglobulin molecule. Although regarded as a component of the hemostatic system, activated platelets release a wide variety of substances involved in inflammation. Platelets are elliptical 2-3 um anuclear structures. They are classified with mononuclear cells for convenience.