A. Neonatal mouse neutrophils (CD11b+, Ly6G+) and macrophages (CD11b+, Ly6G−, F480+) one day after sepsis had decreased ability to produce reactive oxygen species (ROS) in response to PMA stimulation compared to adult mice one day after sepsis (p<0.0001, 2-way ANOVA). B. Functional pathway analysis showed that elderly mice had increased up regulation of genes involved in the synthesis, production, and metabolism of ROS compared to neonatal and/or young adult mice, which is consistent with in vivo results. Heatmaps show the of gene expression of the functional category “Free Radical Scavenging” 2 hours after sepsis in neonatal, young adult, and elderly mice. Orange represents pathways with an over-expression of genes leading to the activation of the pathway and white represents genes that are neither up or down regulated to significance level of p<0.001. Graph shows the various subcategories and their corresponding significance level (Z-score) of up or down regulation.