Cytokines and Chemokines Coordinate the Defense Mechanisms of the Lung
When the lung is injured by infectious agents, an allergic response, or inhalation of toxic particles or gases, an inflammatory process is elicited. Cytokines and Cheniokines are two similar groups of proteins that are produced and released by macrophages, lymphocytes, epithelial and endothelial cells, and various other cells involved in the inflammatory process.
The roles of cytokines and chemokines are to attract inflammatory cells to the site of injury and to provide a means for communication between the cells involved in the inflammatory process. They also are involved in the orchestration of tissue remodeling to promote healing.For example, physical injury to the lung epithelium or the presence of bacteria in the lung causes the release of cytokines tumor necrosis factor (TNF) and interleukin- /(IL-I) from macrophages. These cytokines act to draw neutrophils into the injured area of the lung. In addition, TNF and IL-I initiate mechanisms that cause epithelial cells (e.g., alveolar type II) and endothelial cells to produce the chemokine interleukin-8 (IL-8), which prolongs the inflammatory response and is also a potent chemoattractant of inflammatory ceils. Injured bronchial epithelial cells are also capable of producing IL-1, IL-6, granulocyte-macrophage colony-stimulating factor (GM CSF), and IL-8, all of which have roles in the cascade of inflammation. Other cytokines (IL-4, IL-5, IL-9, IL-13) are involved in allergic inflammation.