Immune aging and pulmonary diseases

Pulmonary immune system, constituted with innate immune and adaptive immune, defenses against pathogens, eliminates senescent cells, and maintains pulmonary physiological homeostasis. The physiological changes in immune system were known as “immune senescence” with increasing age, characterized by increased susceptibility to infection and cancer, reduced response to vaccines, and accompanied by chronic low-grade inflammation. T lymphocytes, B lymphocytes and NK cell immune senescence are the main phenotype of immune senescence. T lymphocytes senescence characterized by immune deficiency and inflammation, caused by thymus degeneration, mitochondrial dysfunction, genetic and epigenetic changes, protein homeostasis imbalance with increasing age. B lymphocytes senescence phenotype is mainly manifested with the decrease of B lymphocytes quantity and quality, and the deficiency in transformation and recombination with increasing age. Meanwhile, with increasing age, NK cells showed changes in cell function, number of cells, and proportion of NK cell subsets. In recent years, a large number of studies have found that the above immune aging changes with increasing age promoted occurrence and development of pulmonary diseases, especially chronic obstructive pulmonary disease (COPD), lung cancer. Even more, there were new therapeutic approach that target to “immunosenescence” have been developed clinically, such as immunotherapy for patients with COPD and lung cancer. However, there are some confusion about the regulatory mechanism of immune senescence in lung diseases and clinical real world. Therefore, this article reviews immune aging, mechanisms of immune aging in the development and progression of lung diseases, mainly included COPD, lung cancer, as well as current immunotherapy targeting to immune senescence, problems, and future directions.