NK Cells Alleviate Lung Inflammation by Negatively Regulating Group 2 Innate Lymphoid Cells

Innate lymphoid cells (ILCs) are a new set of cells considered to be a part of the innate immune system. ILCs are classified into five subsets (according to their transcription factors and cytokine profile) as natural killer cells (NK cells), group 1 ILCs, group 2 ILCs, group 3 ILCs, and lymphoid tissue inducers (LTi). Functionally, these cells resemble the T helper population but lack the expression of recombinant genes, which is essential for the formation of T cell receptors. In this work, the authors address the distinction between peripheral and decidual NK cells, highlighting their diversity in ILC biology and its relevance to human pregnancy. ILCs are effector cells that are important in promoting immunity, inflammation, and tissue repair. Recent studies have directed their attention to ILC actions in pregnancy. Dysregulation or expansion of pro-inflammatory ILC populations as well as abnormal tolerogenic responses may directly interfere with pregnancy, ultimately resulting in pregnancy loss or adverse outcomes. In this review, we characterize these cells, considering recent findings and addressing knowledge gaps in perinatal medicine in the context of ILC biology. Moreover, we discuss the relevance of these cells not only to the process of immune tolerance, but also in disease.

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Androgen signaling negatively controls group 2 innate lymphoid cells

Journal of Experimental Medicine ◽

10.1084/jem.20161807 ◽

2017 ◽

Vol 214 (6) ◽

pp. 1581-1592 ◽

Cited By ~ 95

Author(s):

Sophie Laffont ◽

Eve Blanquart ◽

Magali Savignac ◽

Claire Cénac ◽

Gilles Laverny ◽

...

Keyword(s):

Airway Inflammation ◽

Lung Inflammation ◽

Inflammatory Responses ◽

Allergic Airway Inflammation ◽

Innate Lymphoid Cells ◽

Protective Role ◽

Lymphoid Cells ◽

Peripheral Tissues ◽

Group 2

Prevalence of asthma is higher in women than in men, but the mechanisms underlying this sex bias are unknown. Group 2 innate lymphoid cells (ILC2s) are key regulators of type 2 inflammatory responses. Here, we show that ILC2 development is greatly influenced by male sex hormones. Male mice have reduced numbers of ILC2 progenitors (ILC2Ps) and mature ILC2s in peripheral tissues compared with females. In consequence, males exhibit reduced susceptibility to allergic airway inflammation in response to environmental allergens and less severe IL-33–driven lung inflammation, correlating with an impaired expansion of lung ILC2s. Importantly, orchiectomy, but not ovariectomy, abolishes the sex differences in ILC2 development and restores IL-33–mediated lung inflammation. ILC2Ps express the androgen receptor (AR), and AR signaling inhibits their differentiation into mature ILC2s. Finally, we show that hematopoietic AR expression limits IL-33–driven lung inflammation through a cell-intrinsic inhibition of ILC2 expansion. Thus, androgens play a crucial protective role in type 2 airway inflammation by negatively regulating ILC2 homeostasis, thereby limiting their capacity to expand locally in response to IL-33.

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