The role of basophils in the pathogenesis of allergic disease

There has been much controversy surrounding the importance of basophils in allergy. These cells are, after all, comparatively rare and yet they display remarkable potential to contribute to the symptoms of allergic inflammation. Furthermore, by virtue of their ability to rapidly elaborate T helper type 2 (Th2)-type cytokines, they are well endowed to support ongoing allergic immunity. Despite this, basophils have often been regarded as redundant in this function as in murine models of allergy, their more numerous tissue-fixed mast cell counterparts also display Th2-type cytokine-releasing potential, which is rather different in most human mast cells. Surprisingly, it is from murine models that the basophil has re-surfaced as a key orchestrator of Th2-type immunity and chronic allergic inflammation, a property that has long been hypothesized by researchers into human basophil function but never demonstrated. Moreover, murine experimental models also highlighted the ability of basophils to take up and present antigens in an MHC-dependent manner. Controversy regarding basophils, however, has remained as recent methods for depleting these cells in murine models of allergy and parasitic infection have yielded conflicting results, where the role for this cell oscillates from essential antigen-presenting cells to mere supporting functions in controlling Th2 responses. This review highlights the recent advances in understanding the role of this rather enigmatic cell in allergy.