Figure 7. P. aeruginosa strain PAO1 stimulates neutrophil production of histamine and of transcripts encoding histamine-synthesizing histidine decarboxylase in vitro and in vivo.

(A) Comparison of total histamine content in naïve PMNs purified from BM of uninfected mice, naïve PMNs incubated with P. aeruginosa strain PAO1 in vitro at a 1:10 ratio of PMN:bacteria, and PMNs purified from PAO1-infected lungs 4 h after infection (n=3 animals; *P<0.05 and **P<0.01 compared with naïve PMNs). (B) Effects on HDC transcript levels (relative to HGPRT transcript levels) of incubating PMNs purified from mouse BM with P. aeruginosa strain PAO1 in vitro at a 1:10 ratio of PMN:bacteria. (C) Measurements of HDC transcript levels in PMN obtained in vivo from PAO1-infected mouse lungs. Values were log₁₀ transformed to facilitate graphical comparison of HDC transcript expression in naïve and in vivo-stimulated PMNs. Values represent mean ± se ΔΔC_t values, determined by real-time RT-PCR (n=3; *P<0.05 and **P<0.01 compared with relative HDC transcript levels in PAO1-naïve control PMNs).