CCL2 and chronic obstructive pulmonary disease: The selection of the cytokines assessed in the present study (TNF-α, CCL2, CCL3, CCL4, CCL5, and CXCL1, CXCL5, CXCL8, CXCL9) was based on (i) our previous experiments on human lung parenchyma explants (Buenestado et al., 2013), and (ii) each cytokine’s known role in the pathophysiology of COPD (Morin et al., 2008; Barnes, 2018).