Immunomodulatory mast cells: negative, as well as positive, regulators of immunity.

Mast cells can promote inflammation and other tissue changes in IgE-associated allergic disorders, as well as in certain innate and adaptive immune responses that are thought to be independent of IgE. However, mast cells can also have anti-inflammatory and immunosuppressive functions. Here, we review the evidence that mast cells can have negative, as well as positive, immunomodulatory roles in vivo, and we propose that mast cells can both enhance and later suppress certain features of an immune response.