Role of Common γ-Chain Cytokines in Lung Interleukin-22 Regulation after Acute Exposure to Aspergillus fumigatus.

Abstract

Humans are constantly exposed to the opportunistic mold Aspergillus fumigatus, and disease caused by this pathogen is often determined by the magnitude of local and systemic immune responses. We have previously shown a protective role for interleukin-22 (IL-22) after acute A. fumigatus exposure. Here, employing IL-22Cre R26ReYFP reporter mice, we identified iNKT cells, γδ T cells, and type 3 innate lymphoid cells (ILC3s) as lung cell sources of IL-22 in response to acute A. fumigatus exposure. As these cells often utilize common γ-chain cytokines for their development or maintenance, we determined the role of IL-7, IL-21, and IL-15 in lung IL-22 induction and A. fumigatus lung clearance. We observed that IL-7, IL-21, and IL-15 were essential for, partially required for, or negatively regulated the production of IL-22, respectively. Deficiency in IL-7 and IL-21, but not IL-15R, resulted in impaired fungal clearance. Surprisingly, however, the absence of IL-7, IL-21, or IL-15R signaling had no effect on neutrophil recruitment. The levels of IL-1α, an essential anti-A. fumigatus proinflammatory cytokine, were increased in the absence of IL-7 and IL-15R but decreased in the absence of IL-21. IL-7 was responsible for maintaining lung iNKT cells and γδ T cells, whereas IL-21 was responsible for maintaining lung iNKT cells and ILC3s. In contrast, IL-15R deficiency had no effect on the absolute numbers of any IL-22 cell source, rather resulting in enhanced per cell production of IL-22 by iNKT cells and γδ T cells. Collectively, these results provide insight into how the IL-22 response in the lung is shaped after acute A. fumigatus exposure.