Airway inflammation in asthma is characterized by allergic phenotypes, such as dense infiltration of eosinophils and T helper type 2 lymphocytes, associated with atopic status, while that of COPD is mainly accumulation of neutrophils, CD8-positive cytotoxic T cells, and activated macrophages, which are caused by inhalation of harmful substances, such as smoking. Here, CD8A is linked to chronic obstructive pulmonary disease.