Interleukin-22 in Allergic Airway Diseases: A Systematic Review.

The immune system plays an important role in the pathogenesis of many disorders, including allergic airway diseases. There are studies suggesting that interleukin (IL)-22 can be important in the development of these diseases. However, it is not known if this cytokine acts as proinflammatory or anti-inflammatory agent. This systematic review aimed to analyze level and role of IL-22 in patients with allergic airway diseases in comparison with healthy individuals. Systematic review included only observational studies with patients having allergic rhinitis and/or allergic asthma. The primary outcome measure was IL-22 level in patients with allergic asthma and/or allergic rhinitis. A total of 95 articles were found. Overall, 6 articles were included in systematic review. Five of these studies showed that IL-22 was increased in patients with allergic airway diseases compared with control group. Majority of studies revealed relation between IL-22 level and severity of allergic asthma and allergic rhinitis. Some studies showed positive relation between IL-22 level and total immunoglobulin E (IgE), specific IgE, and eosinophil count in nasal mucosa. IL-22 level is increased in children and adults with allergic airway diseases and is likely to be associated with proinflammatory features.