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Tonsil hyperplasia is the most common cause of pediatric obstructive sleep apnea (OSA). Despite the growing knowledge in tissue immunology of tonsils, the immunopathology driving tonsil hyperplasia and OSA remains unknown. Here we used multi-parametric flow cytometry to analyze the composition and phenotype of tonsillar innate lymphoid cells (ILCs), T cells, and B cells from pediatric patients with OSA, who had previous polysomnography. Unbiased clustering analysis was used to delineate and compare lymphocyte heterogeneity between two patient groups: children with small tonsils and moderate OSA (n = 6) or large tonsils and very severe OSA (n = 13). We detected disturbed ILC and B cell proportions in patients with large tonsils, characterized by an increase in the frequency of naïve CD27 - CD21 hi B cells and a relative reduction of ILCs. The enrichment of naïve B cells was not commensurate with elevated Ki67 expression, suggesting defective differentiation and/or migration rather than cellular proliferation to be the causative mechanism. Finally, yet importantly, we provide the flow cytometry data to be used as a resource for additional translational studies aimed at investigating the immunological mechanisms of pediatric tonsil hyperplasia and OSA., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Carrasco, Sjölander, Van Acker, Dernstedt, Fehrm, Forsell, Friberg, Mjösberg and Rao.)

Although the function of the circulating immune cell compartment has been studied in detail for decades, limitations in terms of access and cell yields from peripheral tissues have restricted our understanding of tissue-based immunity, particularly in humans. Recent advances in high-throughput protein analyses, transcriptional profiling, and epigenetics have partially overcome these obstacles. Innate lymphoid cells (ILCs) are predominantly tissue-resident, and accumulating data indicate that they have significant tissue-specific functions. We summarize current knowledge of ILC phenotypes in various tissues in mice and humans, aiming to clarify ILC immunity in distinct anatomical locations., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

ILCs and T helper cells have been shown to exert bi-directional regulation in mice. However, how crosstalk between ILCs and CD4 + T cells influences immune function in humans is unknown. Here we show that human intestinal ILCs co-localize with T cells in healthy and colorectal cancer tissue and display elevated HLA-DR expression in tumor and tumor-adjacent areas. Although mostly lacking co-stimulatory molecules ex vivo, intestinal and peripheral blood (PB) ILCs acquire antigen-presenting characteristics triggered by inflammasome-associated cytokines IL-1β and IL-18. IL-1β drives the expression of HLA-DR and co-stimulatory molecules on PB ILCs in an NF-κB-dependent manner, priming them as efficient inducers of cytomegalovirus-specific memory CD4 + T-cell responses. This effect is strongly inhibited by the anti-inflammatory cytokine TGF-β. Our results suggest that circulating and tissue-resident ILCs have the intrinsic capacity to respond to the immediate cytokine milieu and regulate local CD4 + T-cell responses, with potential implications for anti-tumor immunity and inflammation.

Background: Group 2 innate lymphoid cells (ILC2s) play a key role in the initiation and maintenance of type 2 immune responses. The prostaglandin (PG) D 2 -chemoattractant receptor-homologous molecule expressed on T H 2 cells (CRTH2) receptor axis potently induces cytokine production and ILC2 migration., Objective: We set out to examine PG production in human ILC2s and the implications of such endogenous production on ILC2 function., Methods: The effects of the COX-1/2 inhibitor flurbiprofen, the hematopoietic prostaglandin D 2 synthase (HPGDS) inhibitor KMN698, and the CRTH2 antagonist CAY10471 on human ILC2s were determined by assessing receptor and transcription factor expression, cytokine production, and gene expression with flow cytometry, ELISA, and quantitative RT-PCR, respectively. Concentrations of lipid mediators were measured by using liquid chromatography-tandem mass spectrometry and ELISA., Results: We show that ILC2s constitutively express HPGDS and upregulate COX-2 upon IL-2, IL-25, and IL-33 plus thymic stromal lymphopoietin stimulation. Consequently, PGD 2 and its metabolites can be detected in ILC2 supernatants. We reveal that endogenously produced PGD 2 is essential in cytokine-induced ILC2 activation because blocking of the COX-1/2 or HPGDS enzymes or the CRTH2 receptor abolishes ILC2 responses., Conclusion: PGD 2 produced by ILC2s is, in a paracrine/autocrine manner, essential in cytokine-induced ILC2 activation. Hence we provide the detailed mechanism behind how CRTH2 antagonists represent promising therapeutic tools for allergic diseases by controlling ILC2 function., (Copyright © 2018 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Escherichia coli and Klebsiella pneumoniae are opportunistic pathogens that are commonly associated with infections at mucosal surfaces, such as the lung or the gut. The host response against these types of infections includes the release of epithelial-derived antimicrobial factors such as lipocalin-2 (LCN-2), a protein that specifically inhibits the iron acquisition of Enterobacteriaceae by binding and neutralizing the bacterial iron-scavenging molecule enterobactin. Regulation of epithelial antimicrobial responses, including the release of LCN-2, has previously been shown to depend on IL-22, a cytokine produced by innate lymphoid cells type 3 (ILC3) during Enterobacteriaceae infections. However, much remains unknown about the extent to which antimicrobial responses are regulated by IL-22 and how IL-22 regulates the expression and production of LCN-2 in intestinal epithelial cells (IECs). Our study demonstrates how IL-22-induced activation of STAT3 synergizes with NF-κB-activating cytokines to enhance LCN-2 expression in human IECs and elucidates how ILC3 are involved in LCN-2-mediated host defense against Enterobacteriaceae. Together, these results provide new insight into the role of ILC3 in regulating LCN-2 expression in human IECs and could prove useful in future studies aimed at understanding the host response against Enterobacteriaceae as well as for the development of antimicrobial therapies against Enterobacteriaceae-related infections., (© 2019 Coorens et al.)

Background: Group 2 innate lymphoid cells (ILC2s) are involved in the initial phase of type 2 inflammation and can amplify allergic immune responses by orchestrating other type 2 immune cells. Prostaglandin (PG) E 2 is a bioactive lipid that plays protective roles in the lung, particularly during allergic inflammation., Objective: We set out to investigate how PGE 2 regulates human ILC2 function., Methods: The effects of PGE 2 on human ILC2 proliferation and intracellular cytokine and transcription factor expression were assessed by means of flow cytometry. Cytokine production was measured by using ELISA, and real-time quantitative PCR was performed to detect PGE 2 receptor expression., Results: PGE 2 inhibited GATA-3 expression, as well as production of the type 2 cytokines IL-5 and IL-13, from human tonsillar and blood ILC2s in response to stimulation with a combination of IL-25, IL-33, thymic stromal lymphopoietin, and IL-2. Furthermore, PGE 2 downregulated the expression of IL-2 receptor α (CD25). In line with this observation, PGE 2 decreased ILC2 proliferation. These effects were mediated by the combined action of E-type prostanoid receptor (EP) 2 and EP4 receptors, which were specifically expressed on ILC2s., Conclusion: Our findings reveal that PGE 2 limits ILC2 activation and propose that selective EP2 and EP4 receptor agonists might serve as a promising therapeutic approach in treating allergic diseases by suppressing ILC2 function., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Vitamin D deficiency is a risk factor for inflammatory bowel disease (IBD). The IL-23-driven tissue-resident group 3 innate lymphoid cells (ILC3s) play essential roles in intestinal immunity, and targeting IL-23/12 is a promising approach in IBD therapy., Objective: We set out to define the role of 1α,25-dihydroxy vitamin D3 (1,25D) in regulating functional responses of human mucosal ILC3s to IL-23 plus IL-1β stimulation., Methods: Transcriptomes of sorted tonsillar ILC3s were assessed by using microarray analysis. ILC3 cytokine production, proliferation, and differentiation were determined by means of flow cytometry, ELISA, and multiplex immunoassay. Intestinal cell suspensions and ILC3s sorted from gut biopsy specimens of patients with IBD were also analyzed along with plasma 25-hydroxy vitamin D3 (25D) detection., Results: ILC3s stimulated with IL-23 plus IL-1β upregulated the vitamin D receptor and responded to 1,25D with downregulation of the IL-23 receptor pathway. Consequently, 1,25D suppressed IL-22, IL-17F, and GM-CSF production from tonsillar and gut ILC3s. In parallel, 1,25D upregulated genes linked to the IL-1β signaling pathway, as well as the IL-1β-inducible cytokines IL-6, IL-8, and macrophage inflammatory protein 1α/β. The 1,25D-triggered skewing in ILC3 function was not accompanied or caused by changes in viability, proliferation, or phenotype. Finally, we confirmed low 25D plasma levels in patients with IBD with active inflammation., Conclusion: In light of the beneficial targeting of IL-23/12 in patients with IBD, 1,25D appears as an interesting therapeutic agent that inhibits the IL-23 receptor pathway, providing a novel mechanism for how ILC3s could be manipulated to regulate intestinal inflammation., (Copyright © 2017 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)