Interleukin 8 concentrations induced by immunoglobulin G of systemic sclerosis patients (SSc-IgG) in supernatants correlate with clinical features of SSc-IgG donors. (A) Correlation of measured interleukin 8 (IL-8) concentrations with the time since Raynaud’s phenomenon onset (26 patients with reported Raynaud’s phenomenon onset) and (B) classification into early and late stages of the disease (0 to 6 years and >6 years since systemic sclerosis (SSc) onset, respectively) by means of the first non-Raynaud’s symptom onset (25 patients with reported first non-Raynaud’s symptom onset). (C) Correlation of measured IL-8 concentrations with the time since onset of pulmonary arterial hypertension (PAH; 10 patients with reported PAH onset) and (D) with the diffusion capacity of the lung for carbon monoxide (DLCO; 23 patients with reported DLCO). IL-8 levels were measured by enzyme-linked immunosorbent assay. Statistical analysis was done by two-tailed Spearman's correlation (A, B and D) and by Mann–Whitney U test (B). Data in (B) are shown as box-and-whisker plot (Tukey). *P < 0.05, **P < 0.01.