Fig. 5
Scatter dot plots of (a) paired synovial fluid (SF) and blood gene expression and (b) protein levels of cytokine expression in patients with psoriatic arthritis (PsA). Chemokine (C-X-C motif) ligand 10 (CXCL10) gene expression was eightfold greater in SF cells (mean ΔCt = 6.55 ± 2.67) than in blood cells (mean ΔCt = 9.55 ± 1.44; p = 0.035 by paired Student’s t test; n = 8). Fold change was calculated using the comparative cycle threshold (ΔΔCt) method, and values are shown as log102−ΔCt values to better visualize the difference between groups (see Methods section of text). In paired SF and serum from 11 patients with PsA, CXCL10 levels were significantly elevated in SF, whereas interferon γ (IFNγ) levels were significantly reduced (p = 0.001 by Wilcoxon signed-rank test). CXCL10 and chemokine (C-X-C motif) receptor 3 (CXCR3) messenger RNA expression were compared in (c) SF and (d) blood, and a significant positive correlation was observed in SF (Spearman’s correlation coefficient = 0.883, p = 0.0031). Asterisks are used to indicate significant differences between groups, where * = p<0.05 and ** = p<0.01. GAPDH Glyceraldehyde 3-phosphate dehydrogenase, IL Interleukin