THE MAST-CELL - A VERSATILE EFFECTOR CELL FOR A CHALLENGING WORLD

Mast cells are phenotypically and functionally versatile effector cell s. When activated by IgE-dependent or other mechanisms, mast cells can produce a diverse array of mediators including TNF-alpha and many oth er cytokines. Moreover mast cells can express increased numbers of hig h-affinity surface receptors for IgE (Fc epsilon RI) and enhanced leve ls of IgE-dependent mediator secretion in response to elevations in co ncentrations of IgE. These characteristics (and others) have suggested diverse potential roles for mast cells in health and disease. To test specific hypotheses about mast cell function in allergic reactions an d other biological responses in vivo, one can employ genetically mast- cell-deficient Kit(W)/Kit(W-v) mice which do or do not contain adoptiv ely transferred mast cell populations derived from genetically compati ble wild-type mice or mice with mutations that influence mast cell bio logy. Such work has already indicated that mast cells (and, in some ca ses, mast-cell-derived cytokines) can have a critical role in the expr ession of the acute, late-phase and chronic components of IgE-dependen t allergic inflammation and can influence the development of an import ant functional consequence of such reactions: airways hyperresponsiven ess. However, mast cells can also perform important beneficial roles i n host defense, both in IgE-dependent immune responses to certain para sites and in natural immunity to bacterial infection.