It has been reported that M1 pro-inflammatory macrophages are the predominant subpopulations in COPD (Chana et al., 2014), secreting many inflammatory mediators including TNF-α, IL-1β, IL-6, IL-12, IL-23, IL-27, CXCL9, CXCL10, CXCL11, CXCL16, CCL5, and ROS (Shapouri-Moghaddam et al., 2018). Here, CXCL9 is linked to chronic obstructive pulmonary disease.