As shown by immunohistochemical analysis of hearts of the patients suffering from cardiomyopathy endothelial cells in the heart express nuclear IL-33 as well as its membrane-bound receptor ST2, whereas cardiac myocytes and vascular smooth muscle cells in the heart stained positive for IL-33 only and were weak positive or negative, respectively, for ST2 confirming our in vitro observations. The gene discussed is IL1RL1; the disease is cardiomyopathy.