IL18 and chronic obstructive pulmonary disease: The P2X7 receptor when exposed to ATP induces a number of features associated with COPD pathogenesis, such as neutrophil chemotaxis, release of proinflammatory cytokines (i.e., IL-1β, IL-6, and IL-18), reactive oxygen species (ROS), and tissue-degrading enzymes from neutrophils and macrophages [25].