['Residual platelet reactivity (RPR) on antiplatelet therapy in ischemic heart disease patients is associated with adverse events. Clinical, cellular and pharmacogenetic factors may account for the variable response to antiplatelet treatment.', 'We sought to explore the interplay of multiple pro-inflammatory and anti-inflammatory cytokines with platelet function in patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI) on dual antiplatelet therapy.', 'In 208 ACS patients undergoing PCI on dual antiplatelet therapy we measured platelet function by platelet aggregation with two agonists [1mM arachidonic acid (AA) and 10muM ADP]. IL-1beta, IL-1ra, IL-4, IL-6, IL-8, IL-10, IL-12, IP-10, IFN-gamma, MCP-1, MIP-1alpha, MIP-1beta, TNF-alpha, and VEGF levels were determined by using the Bio-Plex cytokine assay (Bio-Rad Laboratories Inc., Hercules, CA, USA). We defined patients with RPR those with platelet aggregation by AA >or=20% and/or ADP (10micromol) >or=70%.', 'We documented a significant association between IP-10, IFN-gamma, IL-4 and RPR by both AA- and ADP-induced platelet aggregation after adjustment for age, sex, cardiovascular risk factors, ejection fraction, BMI, vWF and CRP. Patients with pro-inflammatory cytokines not compensated by anti-inflammatory cytokines had higher risk of RPR by both AA and ADP (AA: OR=3.85, 95% CI 1.52-9.74; ADP: OR=2.49, 95% CI 1.33-4.68) with respect to patients with balanced anti-/pro-inflammatory cytokines. Patients with anti-inflammatory response overwhelming pro-inflammatory response have lower risk of RPR (AA: OR=0.55, 95% CI 0.28-1.06; ADP: OR=0.47, 95% CI 0.26-0.87).'] Is the balance between pro- and anti-inflammatory cytokines associated with platelet aggregability in acute coronary syndrome patients?