The eotaxin subfamily of CC chemokines consists of eotaxin-1/CCL11, eotaxin-2/CCL24 and eotaxin-3/CCL26. All eotaxins induce the trafficking of eosinophils to the sites of inflammation via CC chemokine receptor 3 (CCR3), which is also expressed by several different cell types, including basophils, dendritic cells, smooth muscle cells, epithelial cells and fibroblasts. The sequence similarity between the three eotaxins is limited (<40%), but their functional properties are very similar. Eotaxin-1 and -2 are expressed by both haematopoietic and non-haematopoietic cells, but eotaxin-3 expression has been reported to be limited to non-haematopoietic cells. Interleukin (IL)-4 is the main inducer for eotaxin-3 expression, whereas eotaxin-1 is up-regulated by IL-4 and the proinflammatory cytokine tumour necrosis factor (TNF)-α. Eotaxin-3 is expressed in vascular endothelial cells and human dermal fibroblasts after IL-4 and IL-13 stimulation, and this is dependent upon the IL-4-/IL-13-specific transcription factor, signal transducers and activator of transcription (STAT)-6. Eotaxin-3 is expressed on the surface of IL-4-stimulated endothelial cells and promotes eosinophil transmigration.
