Dendritic Cells Promote the Differentiation of ILCs into NCR⁻ILC3s in the Lungs of Mice Exposed to Cigarette Smoke

The involvement of Group 3 innate lymphoid cells (ILC3s) and dendritic cells (DCs) in chronic lung inflammation has been increasingly regarded as the key to understand the inflammatory mechanisms of smoke-related chronic obstructive pulmonary disease (COPD). However, the mechanism underlying the engagement of both remains unclear. Our study aimed to explore NCR⁻ILC3 differentiation in the lungs of mice exposed to cigarette smoke (CS) and to further investigate whether DCs activated by CS exposure contribute to the differentiation of ILCs into NCR⁻ILC3s. The study involved both <i>in vivo</i> and <i>in vitro</i> experiments. In the former, the frequencies of lung NCR⁻ILC3s and NKp46⁻IL-17A⁺ ILCs and the expression of DCs, CD40, CD86, IL-23, and IL-1β quantified by flow cytometry were compared between CS-exposed mice and air-exposed mice. In the latter, NKp46⁻IL-17A⁺ ILC frequencies quantified by flow cytometry were compared after two cocultures, one involving lung CD45⁺Lin⁻CD127⁺ ILCs sorted from air-exposed mice and DCs sifted by CD11c magnetic beads from CS-exposed mice and another including identical CD45⁺Lin⁻CD127⁺ ILCs and DCs from air-exposed mice. The results indicated significant increases in the frequencies of NCR⁻ILC3s and NKp46⁻IL-17A⁺ ILCs; in the expression of DCs, CD40, CD86, IL-23, and IL-1β in CS-exposed mice; and in the frequency of NKp46⁻IL-17A⁺ ILCs after the coculture with DCs from CS-exposed mice. In conclusion, CS exposure increases the frequency of lung ILCs and NCR⁻ILC3s. CS-induced DC activation enhances the differentiation of ILCs into NCR⁻ILC3s, which likely acts as a mediating step in the involvement of NCR-ILC3s in chronic lung inflammation.