The mast cell revisited.

The role of mast cells in allergic reactions is reviewed and the origin, distribution and properties of mast cells are reported. The characteristics of two phenotypically distinct mast cell populations are described. The function and properties of the IgE molecule as an antigen receptor on mast cells is discussed. The IgE receptor and its structure is updated. The participation of mast cells in the acute and late phase of the allergic reaction is pointed out. A double role for mast cells in allergic reactions is suggested: they may be responsible for the acute phase reaction through the release of mediators such as histamine and leukotrienes and for the late phase reaction through the release of pro-inflammatory cytokines.