A. Elderly mice have increased absolute numbers of neutrophils (CD11b+, Ly6G+)(* p<0.0001, One-way ANOVA) and macrophages († P<0.05, One-way ANOVA)(CD11b+, Ly6G−, F480+) in the peritoneum via flow cytometry one day after sepsis, whereas neonates had significantly decreased numbers. (n=7–8)(p=0.001, Tukey’s Multiple Comparisons). Data shown are from two or more independent experiments. B. IPA functional pathway analysis revealed that elderly mice have significantly more upregulation of pathways involved in the recruitment of neutrophils, myeloid cells, and phagocytes, while neonates have minimal upregulation of these same pathways (* Z-score >2). Heat maps show the of gene expression of the functional category “Immune Cell Trafficking-Recruitment” 24 hours following sepsis. Orange represents pathways with an over-expression of genes leading to the activation of the pathway, whereas white represents genes that are neither up or down regulated to significance level of p<0.001.