CCR3 and asthma: During asthma, mast cells and Th2 lymphocytes are activated in the lung to generate IL-4, IL-3 and tumour necrosis factor (TNF)-α.12 These cytokines stimulate the generation of eotaxin, which acting on CC chemokine receptor 3 (CCR3) on eosinophilsthen stimulate the migration of eosinphils into the lung tissue.