CXCL8 and chronic obstructive pulmonary disease: Among those, CXCL8 (IL-8), secreted by T lymphocytes, epithelial cells, smooth muscle cells, and macrophages might especially be important, as CXCL8 (IL-8) is also increased in the airways of patients with some respiratory diseases such as CF, COPD, and asthma [18–22].