Our finding that fractalkine is increased in the left ventricles of EP4 KO mice with impaired cardiac function is in agreement with the findings of Xuan et al [4] who described that fractalkine was increased in heart failure induced by trans-aortic constriction or MI and that the outcome of these disease processes could be improved by a neutralizing antibody to fractalkine. The gene discussed is PTGER4; the disease is myocardial infarction.