CCL2 and chronic obstructive pulmonary disease: Indeed, in the CS group and COPD S1, S2, and S3 groups, several cytokines had serum concentrations greater than the NS group median values in at least two-thirds (≥67%) of the subjects: this was the case for MCP-1 in all four groups (CS and S1–3); for IL-8 in the S1–3; for VEGF in S1 and S2; for IFN-γ, IL-6 and TNFα in S2 and S3; and for IL-17 in S3 only.