Background IL-33,an IL-l-like cytokine,is a ligand for IL1RL1,which is an important effector molecule of type 2 T helper responses.Although IL-33/IL1RL1 interaction has been suggested to be important in the development of atherosclerosis,genetic influences of the polymorphisms of IL33 in human ischemic stroke are unclear.The aim of this study was to examine whether the single nucleotide polymorphisms in IL33 are associated with ischemic stroke in Northern Chinese population.