The Transcription Factor AHR Prevents the Differentiation of a Stage 3 Innate Lymphoid Cell Subset to Natural Killer Cells

• IL-1β maintains a human population of IL-22+ IL-1R1hi ILC3s in SLT by regulating AHR
• Inhibition of AHR in human IL-1R1hi ILC3s promotes NK cell differentiation in vitro
• Expression of AHR prevents human IL-1R1hi ILC3 differentiation to NK cells

SummaryAccumulating evidence indicates that human natural killer (NK) cells develop in secondary lymphoid tissue (SLT) through a so-called “stage 3” developmental intermediate minimally characterized by a CD34−CD117+CD94− immunophenotype that lacks mature NK cell function. This stage 3 population is heterogeneous, potentially composed of functionally distinct innate lymphoid cell (ILC) types that include interleukin-1 receptor (IL-1R1)-positive, IL-22-producing ILC3s. Whether human ILC3s are developmentally related to NK cells is a subject of ongoing investigation. Here, we show that antagonism of the aryl hydrocarbon receptor (AHR) or silencing of AHR gene expression promotes the differentiation of tonsillar IL-22-producing IL-1R1hi human ILC3s to CD56brightCD94+ interferon (IFN)-γ-producing cytolytic mature NK cells expressing eomesodermin (EOMES) and T-Box Protein 21 (TBX21 or TBET). Hence, we demonstrate the lineage plasticity of human ILCs by identifying AHR as a transcription factor that prevents IL-1R1hi ILC3s from differentiating into NK cells.

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