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Innate lymphoid cells (ILCs) are highly plastic and predominantly mucosal tissue-resident cells that contribute to both homeostasis and inflammation depending on the microenvironment. The discovery of naïve-like ILCs suggests an ILC differentiation process that is akin to naïve T cell differentiation. Delineating the mechanisms that underlie ILC differentiation in tissues is crucial for understanding ILC biology in health and disease. Here, we showed that tonsillar ILCs expressing CD45RA lacked proliferative activity, indicative of cellular quiescence. CD62L distinguished two subsets of CD45RA

Innate lymphoid cells (ILCs) are highly plastic and predominantly mucosal tissue-resident cells that contribute to both homeostasis and inflammation depending on the microenvironment. The discovery of naïve-like ILCs suggests an ILC differentiation process that is akin to naïve T cell differentiation. Delineating the mechanisms that underlie ILC differentiation in tissues is crucial for understanding ILC biology in health and disease. Here, we showed that tonsillar ILCs expressing CD45RA lacked proliferative activity, indicative of cellular quiescence. CD62L distinguished two subsets of CD45RA+ILCs. CD45RA+CD62L+ILCs (CD62L+ILCs) resembled circulating naïve ILCs because they lacked the transcriptional, metabolic, epigenetic, and cytokine production signatures of differentiated ILCs. CD45RA+CD62L−ILCs (CD62L−ILCs) were epigenetically similar to CD62L+ILCs but showed a transcriptional, metabolic, and cytokine production signature that was more akin to differentiated ILCs. CD62L+and CD62L−ILCs contained uni- and multipotent precursors of ILC1s/NK cells and ILC3s. Differentiation of CD62L+and CD62L−ILCs led to metabolic reprogramming including up-regulation of genes associated with glycolysis, which was needed for their effector functions after differentiation. CD62L−ILCs with preferential differentiation capacity toward IL-22–producing ILC3s accumulated in the inflamed mucosa of patients with inflammatory bowel disease. These data suggested distinct differentiation potential of CD62L+and CD62L−ILCs between tissue microenvironments and identified that manipulation of these cells is a possible approach to restore tissue-immune homeostasis.

Resident memory T lymphocytes (T

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 naive CD27(-)CD21(hi) B cells and a relative reduction of ILCs. The enrichment of naive 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. De två första författarna delar förstaförfattarskapet.De två sista författarna delar sistaförfattarskapet.

Cross-reactive CD4+ T cells that recognize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are more commonly detected in the peripheral blood of unexposed individuals compared with SARS-CoV-2–reactive CD8+ T cells. However, large numbers of memory CD8+ T cells reside in tissues, feasibly harboring localized SARS-CoV-2–specific immune responses. To test this idea, we performed a comprehensive functional and phenotypic analysis of virus-specific T cells in tonsils, a major lymphoid tissue site in the upper respiratory tract, and matched peripheral blood samples obtained from children and adults before the emergence of COVID-19 (coronavirus disease 2019). We found that SARS-CoV-2–specific memory CD4+ T cells could be found at similar frequencies in the tonsils and peripheral blood in unexposed individuals, whereas functional SARS-CoV-2–specific memory CD8+ T cells were almost only detectable in the tonsils. Tonsillar SARS-CoV-2–specific memory CD8+ T cells displayed a follicular homing and tissue-resident memory phenotype, similar to tonsillar Epstein-Barr virus–specific memory CD8+ T cells, but were functionally less potent than other virus-specific memory CD8+ T cell responses. The presence of preexisting tissue-resident memory CD8+ T cells in unexposed individuals could potentially enable rapid sentinel immune responses against SARS-CoV-2. Title in Web of Science: Identification of resident memory CD8(+) T cells with functional specificity for SARS-CoV-2 in unexposed oropharyngeal lymphoid tissue

While it is generally accepted that tissue-resident memory T lymphocytes protect host tissues from secondary immune challenges, it is unclear whether, and if so, how they contribute to systemic secondary immune responses. Here we show that in human individuals with an established immune memory to measles, mumps and rubella viruses, when challenged with the measles-mumps-rubella (MMR) vaccine again, tissue-resident memory CD4+ T cells are mobilized into the blood within 16 to 48 hours after vaccination. These cells then leave the blood again, and apparently contribute to the systemic secondary immune reaction, as is evident from the representation of mobilized T cell receptor Vβ clonotypes among newly generated circulating memory T lymphocytes, from day 7 onwards. Mobilization of the tissue-resident memory T cells is cognate, in that memory T lymphocytes recognizing other antigens, e.g. tetanus toxin, are not mobilized, unless they cross-react with the vaccine. These data originally demonstrate the essential contribution of tissue-resident memory T cells to secondary systemic immune responses, confirming that immunological memories to systemic pathogens are maintained (also) by tissue-resident memory T cells. In practical terms, the present work defines day 1 to 2 after antigenic challenge as a time window to assess the entire immunological T cell memory for a certain pathogen, including mobilized tissue-resident memory T cells, and its correlates of effectivity.Capsule summaryThe study demonstrates the rapid and cognate mobilization of tissue-resident memory CD4+ T cells into the blood upon antigenic rechallenge, and their contribution to secondary systemic immune responses.

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., Murine ILCs can modulate T cell responses in MHCII-dependent manner. Here the authors show that human ILCs process and present antigens and induce T-cell responses upon exposure to IL-1-family cytokines; along with the article by Lehmann et al, this work elucidates how cytokines set context specificity of ILC-T cell crosstalk by regulating ILC antigen presentation.

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. Funding Agencies|Stiftelsen forStrategisk Forskning [FFL15-0120]; Svenska Sallskapet for Medicinsk Forskning [4-140/2014]; Vetenskapsradet [521-2013-2791]; Knut och Alice Wallenbergs Stiftelse [4-1198/2016]; Cancerfonden [170082, 160664]

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.

It is a matter of current debate whether the bone marrow is a hub for circulating memory T lymphocytes and/or the home of resident memory T lymphocytes. Here we demonstrate for CD69+ murine CD8+ , and CD69+ murine and human CD4+ memory T lymphocytes of the bone marrow, making up between 30 and 60% of bone marrow memory T lymphocytes, that they express the gene expression signature of tissue-resident memory T lymphocytes. This suggests that a substantial proportion of bone marrow memory T lymphocytes are resident. It adds to previous evidence that bone marrow memory T cells are resting in terms of mobility and proliferation, and maintain exclusive long-term memory to distinct, systemic antigens.

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.

Background The human gut mucosal immune system is compartmentalised in distinct and specialised immune niches. The epithelium and the lamina propria have been proposed as effector sites, while gut-associated lymphoid tissues (GALTs) constitute inductive immune niches. The major mucosal GALTs are the Peyer’s patches in the ileum and the colonic isolated lymphoid follicles (ILFs), scattered in the submucosa of the colon. The majority of studies of human gut immune function in health and disease have analysed unfractionated mucosal tissue samples. Hence, in contrast to mice, little is known about compartmentalised immune cell specialisation in the human gut. The aim of this study was to use novel dissection methods to analyse separate human gut immune niches. Methods Macroscopically healthy margins from colorectal cancer colectomies were obtained at a minimum distance of 10 cm from the tumour border. After faeces, mucus, fat and muscle removal, Peyer’s patches were identified and dissected using a stereomicroscope (based on Keita et al., Lab Invest, 2006). Colonic mucosa and submucosa (containing ILFs) fractions were mechanically separated by forceps (based on the method developed by Fenton et al., Immunity, under revision). Isolation of epithelial and lamina propria fractions from the mucosal compartment was performed by calcium chelation (DTT and EDTA) and enzymatic digestion (Collagenase II and DNAse), respectively. Cell suspensions from each fraction were analysed by flow cytometry (BD LSR-Fortessa and BD FACSymphony). Results As expected, mucosal GALTs were characterised by an enrichment of germinal centre B cells (CD19+CD20+CD38+), lymphoid tissue-like innate lymphoid cells (Lin−CD127+CD117+Nrp1+) and a higher CD4+/CD8+ T-cell ratio vs. mucosa, whereas the mucosal fraction was enriched for plasma cells (CD19+CD20−CD38high) and distinguished by a decreased CD4+/CD8+ T-cell ratio as compared with the GALT in both ileum and colon. CD19+/CD3+ ratios were only higher in Peyer’s patches but not in colonic submucosa enriched with ILFs, possibly due to the smaller size of the B-cell follicles in the latter. The intraepithelial compartment lacked B cells and contained more γδ-T cells as compared with the GALT and lamina propria. Conclusion We have used novel dissection methods in human intestinal tissues that reveal a compartmentalised immune cell specialisation that is in line with what has previously been described in mice. The method will allow for future deeper analysis of the human gut immune niches in health and disease, such as in inflammatory bowel disease.

It is a matter of current debate whether the bone marrow is a hub for circulating memory T lymphocytes and/or the home of resident memory T lymphocytes. Here we demonstrate for CD69+ murine CD8+, and CD69+ murine and human CD4+ memory T lymphocytes of the bone marrow, making up between 30 and 60% of bone marrow memory T lymphocytes, that they express the gene expression signature of tissue‐resident memory T lymphocytes. This suggests that a substantial proportion of bone marrow memory T lymphocytes are resident. It adds to previous evidence that bone marrow memory T cells are resting in terms of mobility and proliferation, and maintain exclusive long‐term memory to distinct, systemic antigens.

The role of microfossils for the ceramic paste characterization has been revealed through firing experiment. Ceramic samples were prepared with the clay of Monte San Giorgio (Sicily, Italy), that contains many microfossils that suffered relevant changes in the microstructure and chemical composition during firing temperature. The samples were fired at different conditions according to the presumed ancient techniques. The alteration and/or decomposition of mineral phases with temperature was observed with optical and electron microscopy by monitoring the mineral modifications at different firing conditions. In order to validate our approach on archaeological material, the analyses were performed also on ceramic fragments, furnished by the Ceramics Regional Museum “Antonino Ragona” of Caltagirone. The micropaleontological study, as component of the archaeometric analyses, seems to be a useful archaeothermometry for the evaluation of firing processes and sometimes decisive to distinguish the characteristics of the clay used in a given production.

Group 2 innate lymphoid cells (ILC2s) play a key role in the initiation and maintenance of type 2 immune responses. The prostaglandin (PG) DWe set out to examine PG production in human ILC2s and the implications of such endogenous production on ILC2 function.The effects of the COX-1/2 inhibitor flurbiprofen, the hematopoietic prostaglandin DWe show that ILC2s constitutively express HPGDS and upregulate COX-2 upon IL-2, IL-25, and IL-33 plus thymic stromal lymphopoietin stimulation. Consequently, PGDPGD

Innate lymphoid cells (ILCs) are a type of immune cell that are considered to be tissue-resident gatekeepers situated in mucosal membranes, where they contribute to both homeostasis and pathology ( 1 ). In healthy individuals, ILCs are involved in tissue repair, but ILCs have also been shown to participate in several types of inflammation, including allergy and asthma. Whereas ILCs can be found at low frequencies in the blood circulation, mucosal barriers such as the intestine and airways are enriched for ILCs ( 1 ). However, whether ILCs are in fact tissue resident in the sense that they self-renew without substantial replenishment from other organs has been a topic of debate. The mechanisms of ILC circulation are important for understanding various types of inflammatory conditions and how they can be treated. On page 114 of this issue, Huang et al. ( 2 ) demonstrate that ILC2s are not obligate tissue-resident cells because they can be recruited from the gut to the lung and other organs in response to inflammatory signaling.

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 he ...

The Ikaros family of transcription factors (TFs) are important regulators of lymphocyte function. However, their roles in human innate lymphoid cell (ILC) function remain unclear. Here, we found that Ikaros (IKZF1) is expressed by all ILC subsets, including NK cells, in blood, tonsil and gut, while Helios (IKZF2) is preferentially expressed by ILC3 in tonsil and gut. Aiolos (IKZF3) followed the expression pattern of T-bet and Eomes, being predominantly expressed by ILC1 and NK cells. Differentiation of IFN-γ-producing ILC1 and NK cells from ILC3 by IL-1β plus IL-12-stimulation was associated with upregulation of T-bet and Aiolos. Selective degradation of Aiolos and Ikaros by lenalidomide suppressed ILC1 and NK cell differentiation and expression of ILC1 and NK cell-related transcripts (LEF1, PRF1, GRZB, CD244, NCR3, IRF8). In line with reduced ILC1/NK cell differentiation we observed an increase in the expression of the ILC3-related TF Helios, as well as ILC3 transcripts (TNFSF13B, IL22, NRP1 and RORC) and in the frequency of IL-22 producing ILC3 in cultures with IL-1β and IL-23. These data suggest that suppression of Aiolos and Ikaros expression inhibits ILC1 and NK cell differentiation while ILC3 function is maintained. Hence, our results open up for new possibilities in targeting Ikaros family TFs for modulation of type 1/3 immunity in inflammation and cancer.

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) E2 is a bioactive lipid that plays protective roles in the lung, particularly during allergic inflammation. Objective We set out to investigate how PGE2 regulates human ILC2 function. Methods The effects of PGE2 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 PGE2 receptor expression. Results PGE2 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, PGE2 downregulated the expression of IL-2 receptor α (CD25). In line with this observation, PGE2 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 PGE2 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., Graphical abstract

The Reduction of o-Nitrotoluene