Group 2 innate lymphoid cells (ILC2s): The spotlight in asthma pathogenesis and lung tissue injury.

Asthma is a heterogeneous disease with ranging etiology and severity. Asthma is a disease of chronic inflammation of the airways, with clinical symptoms of wheezing, breathlessness, cough, and chest tightness manifested as chronic fixed or variable airflow obstruction and airway hyperresponsiveness that predispose the airway epithelium to repeated injury, repair, and regeneration. In recent years, innate lymphoid cells (ILC1, ILC2, and ILC3) have been discovered. The predominant ILC type found in the lung tissue is group 2 innate lymphoid cells (ILC2s). Upon damage to the airway epithelium mediating the release of epithelial cytokines (TSLP, IL-33, and IL-25) ensued the activation of ILC2 in an antigen-independent manner. Activated ILC2 produces a significant amount of type 2 cytokines (IL-4, IL-5, IL-9, and IL-13), altogether contributing to type 2 inflammation in the airways. ILC2s are mediators of type 2 immunity for many type 2 inflammatory diseases such as asthma, since ILC2s were reported to play an important role in asthma pathogenesis. Here we discuss the role of ILC2 in the development of asthma and ILC2 effector cytokines (IL-4, IL-5, and IL-13) contributing to airway epithelial structural changes.