Basophils beyond effector cells of allergic inflammation.

Despite being first described in humans nearly 130 years ago, the basophil granulocyte has received little recognition other than being the least common leukocyte circulating in blood. Even after its identity as the source of histamine released by blood cells in response to reaginic IgE, its role in allergic disease has largely been viewed as redundant to that of the tissue mast cell. This line of thought, however, is changing with evidence that has emerged during the last 15 years. Not only have these rare cells been shown to constitute a significant source of cytokines (IL-4 and IL-13) vital to the pathogenesis of allergic disease, but by doing so, may very well modulate T-helper 2-type inflammation at the level of T-cell/dendritic cell interactions. This novel concept combined with the fact that basophils selectively infiltrate allergic lesion sites has sparked greater interest in this once overlooked immune cell, both in adaptive as well as in innate immunity.