Emerging roles of innate lymphoid cells in inflammatory diseases: Clinical implications.

Innate lymphoid cells (ILC) represent a group of lymphocytes that lack specific antigen receptors and are relatively rare as compared to adaptive lymphocytes. ILCs play important roles in allergic and nonallergic inflammatory diseases due to their location at barrier surfaces within the airways, gut, and skin, and they respond to cytokines produced by activated cells in their local environment. Innate lymphoid cells contribute to the immune response by the release of cytokines and other mediators, forming a link between innate and adaptive immunity. In recent years, these cells have been extensively characterized and their role in animal models of disease has been investigated. Data to translate the relevance of ILCs in human pathology, and the potential role of ILCs in diagnosis, as biomarkers and/or as future treatment targets are also emerging. This review, produced by a task force of the Immunology Section of the European Academy of Allergy and Clinical Immunology (EAACI), encompassing clinicians and researchers, highlights the role of ILCs in human allergic and nonallergic diseases in the airways, gastrointestinal tract, and skin, with a focus on new insights into clinical implications, therapeutic options, and future research opportunities.

Innate lymphoid cells in graft-versus-host disease.

Innate lymphoid cells (ILC) are lymphocytes lacking rearranged antigen receptors such as those expressed by T and B cells. ILC are important effector and regulatory cells of the innate immune system, controlling lymphoid organogenesis, tissue inflammation, and homeostasis. The family of ILC consists of cytotoxic NK cells and the more recently described noncytotoxic group 1, 2, and 3 ILC. The classification of noncytotoxic ILC-in many aspects-mirrors that of T helper cells, which is based on the expression of master transcription factors and signature cytokines specific for each subset. The IL-22 producing RORγt(+) ILC3 subset was recently found to be critical in the prevention of intestinal graft-versus-host disease (GVHD) following allogeneic hematopoietic cell transplantation (HCT) via strengthening the intestinal mucosal barrier. In this review, we summarize the current view of the immunological functions of human noncytotoxic ILC subsets and discuss the potentially beneficial features of IL-22 producing ILC3 in improving allo-HCT efficacy by attenuating susceptibility to GVHD. In addition, we explore the possibility of other ILC subsets playing a role in GVHD.

Update on innate lymphoid cells in atopic and non-atopic inflammation in the airways and skin.

Innate lymphoid cells (ILC) is the collective term for a group of related innate lymphocytes, including NK cells and the more recently appreciated non-NK ILC (ILC1, ILC2 and ILC3). ILC all depend on the common γ-chain of the IL-2 receptor and the transcription factor Id2. Furthermore, ILC lack rearranged antigen-receptors such as those expressed by T and B cells. Recent data indicate that non-NK ILC contribute to a wide range of homeostatic and pathophysiological processes primarily by virtue of cytokine production. A lot of effort has been put into understanding the role for the non-NK ILC in mucosal homeostasis, including in the gut and lungs. Recent reports also point towards a role for ILC in skin inflammation. In the lung, ILC may propagate stromal-derived danger signals, with subsequent induction of mainly type 2 cytokine production. This might represent an early trigger of type 2-mediated pathology, which subsequently also engages the adaptive immune system. Similarly, in the skin, ILC are well placed to sense keratinocyte-derived danger signals in an antigen-independent manner. Recent findings link ILC2 to atopic dermatitis and ILC3 to psoriasis. In this review, we provide an updated perspective on the role for non-NK ILC in atopic and non-atopic inflammation in the airways as well as in the skin.

Transcriptional characteristics of CD4+ T cells in multiple sclerosis: relative lack of suppressive populations in blood.

BACKGROUND: Multiple sclerosis (MS) is hypothetically caused by autoreactive Th1 and Th17 cells, whereas Th2 and regulatory T cells may confer protection. The development of Th subpopulations is dependant on the expression of lineage-specific transcription factors. OBJECTIVE: The aim of this study was to assess the balance of CD4(+)T cell populations in relapsing-remitting MS. METHODS: Blood mRNA expression of TBX21, GATA3, RORC, FOXP3 and EBI3 was assessed in 33 patients with relapsing-remitting MS and 20 healthy controls. In addition, flow cytometry was performed to assess T lymphocyte numbers. RESULTS: In relapsing-remitting MS, diminished expression of FOXP3 (Treg) was found (p < 0.05), despite normal numbers of CD4(+)CD25(hi)Treg. Immunoregulatory EBI3 and Th2-associated GATA3 ([a-z]+) was also decreased in MS (p < 0.005 and p < 0.05, respectively). Expression of TBX21 (Th1) and RORC (Th17) did not differ between patients and controls. Similar changes were observed when analysing beta-interferon treated (n = 12) or untreated (n = 21) patients. Analysis of transcription factor ratios, comparing TBX21/GATA3 and RORC/FOXP3, revealed an increase in the RORC/FOXP3 ratio in patients with relapsing-remitting MS (p < 0.005). CONCLUSION: Our findings indicate systemic defects at the mRNA level, involving downregulation of beneficial CD4(+)phenotypes. This might play a role in disease development by permitting activation of harmful T cell populations.

The roles for innate lymphoid cells in the human immune system.

From constituting a novel and obscure cell population, innate lymphoid cells (ILCs) are now accepted as a self-evident part of the immune system, contributing with unique and complementary functions to immunity by production of effector cytokines and interaction with other cell types. In this review, we discuss the redundant and complementary roles of the highly plastic human ILCs and their interaction with other immune cells with the ultimate aim of placing ILCs in a wider context within the human immune system.

Innate lymphoid cells in inflammatory bowel diseases.

It is generally believed that inflammatory bowel diseases (IBD) are caused by an aberrant immune response to environmental triggers in genetically susceptible individuals. The exact contribution of the adaptive and innate immune system has not been elucidated. However, recent advances in treatments targeting key inflammatory mediators such as tumour necrosis factor highlight the crucial role of the innate immune system in IBD. Innate lymphoid cells (ILCs) have recently been identified to play an important role in immune mediated inflammatory diseases. In this review we recapitulate the current knowledge on ILCs in IBD.