CCL2 and chronic obstructive pulmonary disease: In the validation of 148 COPD cases, serum monocyte chemoattractant protein-1 (MCP-1) and IL-1beta levels in cases of PH-associated COPD with mPAP ≥ 25 mmHg were not different from the levels in the no-PH group, while serum IL-6 levels were significantly elevated in the PH group.