The biology of the mast cell.

Mast cells are ancient, versatile immune effector cells. On the one hand, they are endowed with unique effector capabilities and activation responses that initiate innate immunity to bacteria and are essential to host defense against helminthic parasites. On the other hand, they are the major effector of type I hypersensitivity and an important participant in a number of disease processes. This review focuses on the mechanisms of mast cell development, the cytokine control of this process, and the amplification of mast cell effector systems as an important determinant of disease.