A-C, NE is associated with ancillary biomarkers that are relevant to pathobiological features. A, Scatterplots showing the relationship of NE and elafin to circulating neutrophil counts (percentage and absolute) and BMPR2 messenger RNA expression levels in blood (real-time quantitative reverse transcriptase polymerase chain reaction measurements quantified by ΔΔCT method, relative to the GAPDH gene). Spearman ρ and associated P values are shown. Data are from patients who had measurements of neutrophil counts (n = 120/249) or BMPR2 expression (n = 177/249) on the same day as NE and elafin levels. B, Box-and-whisker plots displaying neutrophil counts and BMPR2 expression among patients with increased NE levels (> 134.8 ng/mL, the PAH discrimination cutoff from Fig 1C) vs those with normal NE levels. C, Cytokine fold-changes (immunoassay-detected MFI) in patients with increased NE levels relative to those with normal NE levels. Only same-day measurements were captured (n = 228/249). ∗Differentially expressed cytokines (false-discovery rate < 0.05 in significance analysis of microarrays). BMPR2 = bone morphogenetic protein receptor 2; bNGF = nerve growth factor beta; CCL = C-C motif chemokine ligand; CTACK = cutaneous T-cell-attracting chemokine; CXCL = C-X-C motif chemokine ligand; ΔΔCT = delta delta cycle threshold; FGFb = fibroblast growth factor basic; GAPDH = glyceraldehyde 3-phosphate dehydrogenase; GCSF = granulocyte colony stimulating factor; GMCSF = granulocyte macrophage colony stimulating factor; IFN (a2 or g) = interferon-(alpha2 or gamma); HGF = hepatocyte growth factor; IL = interleukin; IL1 (a, b, or Ra) = IL-1 (alpha, beta, or receptor antagonist); IL12 (p40 or p70) = IL-12 (subunit p40 or p70); IL2Ra = IL-2 receptor subunit alpha; LIF = leukemia inhibitory factor; MCSF = macrophage colony stimulating factor; MIF = macrophage migration inhibitory factor; MFI = median fluorescence intensity; NE = neutrophil elastase; PDGF = platelet-derived growth factor; RANTES = regulated on activation, normal T-cell expressed and secreted; SCF = stem cell factor; SCGFb = stem cell growth factor beta; TNF (a or b) = tumor necrosis factor-(alpha or beta); TRAIL = TNF-related apoptosis-inducing ligand; VEGF = vascular endothelial growth factor.