CD109 and pulmonary emphysema: Regarding the upregulated DEGs in COPD, CD109, B cell linker (BLNK), interleukin-1 receptor type 1 (IL1R1), CD1A, and carboxypeptidase A3 (CPA3) are related to T-helper cell type 2 (Th2) inflammation, but not to emphysema formation.