Functional heterogeneity in the basophil cell lineage.

CD4(+) T-helper type 2 (Th2) cells, characterized by their expression of interleukin (IL)-4, IL-5, IL-9, and IL-13, are required for immunity to helminth parasites and promote the pathological inflammation associated with asthma and allergic diseases. Recent reports from a number of laboratories have indicated that basophils can influence the induction and/or effector stages of Th2 cytokine-mediated inflammation. However, the impact of basophils appears to depend on the anatomical location and nature of the infectious or inflammatory stimulus. This review highlights the factors that regulate basophil development and activation and describes known basophil effector functions. Further, we discuss the recent identification of phenotypic and functional heterogeneity within murine and human basophil populations and discuss how these findings may explain the context-dependent influence of basophils on either the propagation, regulation, or effector phases of Th2 cytokine-associated inflammation.