Mouse CCR3, a member of the family of G-protein– coupled receptors with seven transmembrane spanning domains.In addition to being the major receptor for CCL11, CCR3 also binds to CCL8 (MCP2), CCL7 (MARK), CCL5 (RANTES), CCL24 (eotaxin-2), CCL26 (eotaxin-3), CCL15 (MIP5), and CCL28 (1). In humans, an additional chemokine (CCL13/MCP-4) binds CCR3. This receptor has been found predominantly on leukocytes, including eosinophils, basophils, mast cells, TH2 cells, human dendritic cells, and thymocytes. CCR3 is also present on non-hematopoietic cells, such as brain microglial cells, airway epithelia cells, and human brain and microvascular endothelial cells (2, 3). Studies in bleomycin-induced lung fibrosis suggested that CCL11 and CCR3 play an important role in the development of fibrosis (4). CCR3 is constitutively expressed in cultured lung and primary bronchial fibroblasts and colocalizes with specific surface markers for human fibroblasts in lung tissue. Eotaxin/CCL11 has a direct and selective profibrogenic effect on lung and bronchial fibroblasts (5).