Quantitative PCR analysis of neutrophil chemokines and receptors in paws of male DBA/1 mice aged 12 and 16 weeks. The expression levels of Cxcr1 (A), Cxcr2 (B), Cxcl1 (C) and Gcp2 (D) are shown. Y-axis displays gene expression values normalized to GAPDH and is presented as log-scale (* 10-4). The average gene expression for each gene in both groups is presented by the horizontal line. PCR, polymerase chain reaction.