Effects of Air Pollution on Lung Innate Lymphoid Cells: Review of In Vitro and In Vivo Experimental Studies
Facultad de Ciencias Médicas, Universidad Central del Ecuador, Quito 170521, Ecuador
Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA 02111, USA
Department of Epidemiology, Erasmus Medical Center, 3015GD Rotterdam, The Netherlands
Department of Immunology, Erasmus Medical Center, 3015GD Rotterdam, The Netherlands
Author to whom correspondence should be addressed.
Int. J. Environ. Res. Public Health 2019, 16(13), 2347; https://doi.org/10.3390/ijerph16132347
Received: 11 June 2019 / Revised: 28 June 2019 / Accepted: 29 June 2019 / Published: 2 July 2019
(This article belongs to the Section Environmental Health)
Outdoor air pollution is associated with respiratory infections and allergies, yet the role of innate lymphoid cells (ILCs) in pathogen containment and airway hyperresponsiveness relevant to effects of air pollutants on ILCs is poorly understood. We conducted a systematic review to evaluate the available evidence on the effect of outdoor air pollutants on the lung type 1 (ILC1) and type 2 ILCs (ILC2) subsets. We searched five electronic databases (up to Dec 2018) for studies on the effect of carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2), diesel exhaust particles (DEP), ozone (O3), and particulate matter (PM) on respiratory ILCs. Of 2209 identified citations, 22 full-text papers were assessed for eligibility, and 12 articles describing experimental studies performed in murine strains (9) and on human blood cells (3) were finally selected. Overall, these studies showed that exposure to PM, DEP, and high doses of O3 resulted in a reduction of interferon gamma (IFN-γ) production and cytotoxicity of ILC1. These pollutants and carbon nanotubes stimulate lung ILC2s, produce high levels of interleukin (IL)-5 and IL-13, and induce airway hyperresponsiveness. These findings highlight potential mechanisms by which human ILCs react to air pollution that increase the susceptibility to infections and allergies.