Previous studies have demonstrated that circulating neutrophils (PMNs) contribute to the pathophysiology of myocardial ischemia-reperfusion (MI/R) injury. PMN-endothelial cell interactions are highly regulated by adhesive interactions between PMN CD11/CD18 and coronary endothelial cell intercellular adhesion molecule-1 (ICAM-1). We investigated the effects of MI/R in wild-type, CD18-, and ICAM-1-deficient (-/-) mice. Wild-type (n = 6), CD18 -/- (n = 6), and ICAM-1 -/- (n = 6) mice were subjected to 30 min of myocardial ischemia and 120 min of reperfusion to determine the extent of PMN infiltration and myocardial cell necrosis. Myocardial infarction (% of the area at risk) was 45.1 +/- 5.9 in wild-type mouse hearts. In contrast, the extent of myocardial infarction was significantly (P < 0.05) reduced in the CD18 (19.3 +/- 5.1%)- and ICAM-1 (17.9 +/- 3.2%)-deficient mice. Similarly, PMN infiltration into the ischemic-reperfused myocardium was attenuated by 54% in the CD18 -/- mice and by 32% in ICAM-1 -/- mice compared with wild-type hearts. Deficiency in either CD18 or ICAM-1 expression results in a marked reduction in PMN accumulation and myocardial necrosis after acute MI/R.