CXCL8 and chronic obstructive pulmonary disease: As illustrated in Figure 1, the IL-8 levels increased sequentially from controls [9.45 pg/mL (ranged: 6.85–38.4)], to stable COPD [51.60 pg/mL (ranged: 22.4–131.1)] and COPD exacerbations [129 pg/mL (ranged: 57.7–374)].