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Plasmacytoid dendritic cells (pDCs) sense microbial products through TLR-7 and -9 and translate this sensing in Interferon-α (IFN-α) production and T-cell polarization. The understanding of the mechanisms involved in pDCs stimulation may contribute to immunotherapeutic strategies aiming to decrease HIV-1 reservoir. Here, we characterize the immunomodulatory effects of TLR agonist stimulations through a pDC/T-cell coculture in different HIV-1 disease progression phenotypes and healthy donors (HD). pDCs were previously stimulated with AT-2-HIV-1, CpGA, CpGC and GS9620. After coculture with autologous CD4 or CD8 T-cells we observed an increase of pDCs activation markers levels, interferon related genes, HIV-1 restriction factors and cytokines levels. This pDCs coordinate activation was prominent with CpGC and GS9620 and induced an increase of HIV-specific T-cell response. These results shed light on the mechanisms associated with TLR-specific pDCs stimulation associated with T cell polarization for eliciting antiviral response which is essential for HIV eradication strategies.

Plasmacytoid dendritic cells (pDCs) sense viral and bacterial products through Toll-like receptor (TLR)-7 and -9 and translate this sensing in Interferon-α (IFN-α) production and T cell polarization. These cells are considered a link between innate and adaptive immunity, inducing and maintaining antigen-specific T cell responses and contributing to the control and eventually to the chronic immune activation and disease progression in HIV-1 infection scenario. The understanding of the mechanisms involved in pDCs stimulation may contribute to immunotherapeutic strategies aiming to decrease HIV-1 reservoir. The objective of the present study was to characterize the immunomodulatory effects of TLR agonist stimulations through a pDC/T cell coculture in different HIV-1 disease progression phenotypes and healthy donors (HD). pDCs were previously stimulated with AT-2-HIV-1, CpGA, CpGC and GS9620. After coculture with autologous CD4 or CD8 T cells we observed an increase of pDCs activation markers levels, interferon related genes, HIV-1 restriction factors and cytokines levels. This pDCs coordinate activation was prominent with CpG-C and GS9620 and induced an increase of HIV-specific T cell response. This pDCs dependent HIV-1 specific T-cell response was associated with the upregulation of HIV-1 restriction factors and IFN-α production. Interestingly, pDCs activation in people on ART was similar to that found in people that spontaneously control the virus. These results shed light on the mechanisms associated with TLR-specific pDCs stimulation associated with T cell polarization for eliciting antiviral response which is essential for HIV eradication strategies.

CD300a receptor is found on different CD8+ T cell subsets and its expression has been associated to a more cytotoxic molecular signature. CD300a has an important role in some viral infections and its expression levels are known to be modulated by human immunodeficiency virus (HIV)−1 infection on several cell types. The main objective of this work was to investigate CD300a expression and its regulation during HIV-1 specific CD8+ T cell responses. CD300a receptor expression was analysed by multiparametric flow cytometry on CD8+ T lymphocytes from HIV negative donors, naive HIV-1+ individuals and HIV-1+ subjects under suppressive combined antiretroviral therapy (cART). HIV-1 specific CD8+ T cell response was studied by stimulating cells with HIV-1 derived peptides or with a Gag HIV-1 peptide. Our results showed that HIV-1 specific CD8+ T cells expressing higher levels of CD300a were more polyfunctional showing an increased degranulation and cytokine production. Moreover, we observed an up-regulation of CD300a expression after Gag HIV-1 peptide stimulation. Finally, our results demonstrated an inverse correlation between CD300a expression on CD8+ T lymphocytes and HIV disease progression markers. In conclusion, CD300a expression is associated to a better and more polyfunctional HIV-1 specific CD8+ T cell response., This study was supported by a grant from “Plan Estatal de I+ D+ I 2013–2016, ISCIII-Subdirección de Evaluación y Fomento de la Investigación-Fondo Europeo de Desarrollo Regional (FEDER) (Grant PI13/00889)” and Marie Curie Actions, Career Integration Grant, European Commission (Grant CIG 631674). Joana Vitallé and Iñigo Terrén are recipients of a predoctoral contract funded by the Department of Education, Basque Government (PRE_2017_2_0242 and PRE_2018_1_0032). Joana Vitallé and Iñigo Terrén are recipients of a fellowship from the Jesús de Gangoiti Barrera Foundation (FJGB15/008 and FJGB17/003). Laura Tarancón-Díez was supported by Instituto de Salud Carlos III, PFIS (FI00/00431). Olatz Zenarruzabeitia is recipient of a postdoctoral contract funded by “Instituto de Salud Carlos III-Contratos Sara Borrell 2017 (CD17/0128)” and the European Social Fund (ESF)-The ESF invests in your future. Ezequiel Ruiz-Mateos is supported by Programa Nicolás Monardes, C0032-2017, Consejería de Salud y Bienestar Social, Junta de Andalucía. Francisco Borrego is an Ikerbasque Research Professor, Ikerbasque, Basque Foundation for Science.

Natural killer (NK) cells are lymphocytes with potent antitumor functions and, therefore, multiple NK cell-based cancer immunotherapies have been developed and are currently being tested. However, there is a necessity to find new means to improve these therapies, and immunometabolism represents an attractive target. NK cell effector functions are intricately linked to their metabolism, and modulating the latter could be the key to release their full potential. In this review, we have summarized how NK cell metabolism is regulated during some processes, such as maturation, viral infection, and cytokine stimulation. Additionally, we provide an overview of how NK cell metabolism is affected by current therapeutic approaches aimed to promote NK cell expansion and/or to increase their effector functions. We have also recapitulated several strategies that could help alleviating the metabolic impairment that characterizes tumor-infiltrating NK cells, and thus increase or restore their effector functions. Furthermore, we have reviewed several therapeutic approaches targeting cancer metabolism that could synergize with NK cell-based cancer immunotherapies, and thus enhance their efficacy.

Human CD300a is known to promote the infection by dengue and other enveloped viruses and is overexpressed on CD4+ T cells from HIV-1-infected patients. We found that infected CD4+RA− T cells from untreated HIV-1-infected patients were mostly CD300a+. Furthermore, CD300a expressing CD4+RA− T cells from healthy donors were significantly more infected by HIV-1 in vitro than CD300a− cells. CD300a might represent a biomarker of susceptibility to HIV-1 infection on memory CD4+ T lymphocytes.

The immune factors associated with impaired SARS-CoV-2 vaccine response in the elderly are mostly unknown. We studied old and young people vaccinated with SARS-CoV-2 BNT162b2 mRNA before and after the first and second dose. Aging was associated with a lower anti-RBD IgG levels and a decreased magnitude and polyfunctionality of SARS-CoV-2 specific T cell response. The dramatic decrease in thymic function in the elderly, which fueled alteration in T cell homeostasis, and lower CD161+ T cell levels were associated with decreased T cell response two months after vaccination. Additionally, a deficient dendritic cell (DC) homing, activation and Toll like receptor (TLR)-mediated function, along with a proinflammatory functional profile in monocytes, were observed in the elderly, which was also related to lower specific T cell response after vaccination. These findings might be relevant for the improvement of the current vaccination strategies and for the development of new vaccine prototypes., This study was funded by Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades, Junta de Andalucia (CV20-85418 and P20_00906, DOC-01659 and DOC-00963); Consejeria de Salud, Junta de Andalucia (RH-0037-2020), Instituto de Salud Carlos III (CP19/00159, FI17/00186, FI19/00083, PI19/01172, CM20/00243) Fondos FEDER, and National Spanish Research Council (CSIC).

Natural Killer (NK) cells acquire memory-like properties following a brief stimulation with IL-12, IL-15 and IL-18. These IL-12/15/18-preactivated NK cells, also known as cytokine-induced memory-like (CIML) NK cells, have been revealed as a powerful tool in cancer immunotherapy due to their persistence in the host and their increased effector functions. Several studies have shown that NK cells modulate their metabolism in response to cytokine-stimulation and other stimuli, suggesting that there is a link between metabolism and cellular functions. In this paper, we have analyzed metabolic changes associated to IL-12/15/18-stimulation and the relevance of glycolytic pathway for NK cell effector functions. We have found CIML NK cells are able to retain a metabolic profile shifted towards glycolysis seven days after cytokine withdrawal. Furthermore, we found that treatment with 2-DG differently affects distinct NK cell effector functions and is stimuli-dependent. These findings may have implications in the design of NK cell-based cancer immunotherapies.

Natural Killer (NK) cells acquire memory-like properties following a brief stimulation with IL-12, IL-15 and IL-18. These IL-12/15/18-stimulated NK cells, also known as cytokine-induced memory-like (CIML) NK cells, have been revealed as a powerful tool in cancer immunotherapy due to their persistence in the host and their increased effector functions. Several studies have shown that NK cells modulate their metabolism in response to cytokine-stimulation and other stimuli, suggesting that there is a link between metabolism and cellular functions. In this paper, we have analyzed metabolic changes associated to IL-12/15/18-stimulation and the relevance of glycolytic pathway for NK cell effector functions. We have found that CIML NK cells are able to retain increased glycolytic machinery seven days after cytokine withdrawal. Furthermore, we found that glycolytic inhibition with 2-DG is stimuli-dependent and that differently affects to distinct effector functions. These findings may have implications in the design of NK cell-based cancer immunotherapies.

Allergy is the host immune response against non-infectious substances called allergens. The prevalence of allergic diseases is increasing worldwide. However, while some drugs counteract the symptomatology caused by allergic reactions, no completely effective treatments for allergic diseases have been developed yet. In this sense, the ability of surface activating and inhibitory receptors to modulate the function of the main effector cells of allergic responses makes these molecules potential pharmacological targets. The CD300 receptor family consists of members with activating and inhibitory capabilities mainly expressed on the surface of immune cells. Multiple studies in the last few years have highlighted the importance of CD300 molecules in several pathological conditions. This review summarizes the literature on CD300 receptor expression, regulation and function in mast cells, basophils and eosinophils, the main players of allergic responses. Moreover, we review the involvement of CD300 receptors in the pathogenesis of certain allergic diseases, as well as their prospective use as therapeutic targets for the treatment of IgE-dependent allergic responses.

Summary Natural killer (NK) cells are usually identified by the absence of other lineage markers, due to the lack of cell-surface-specific receptors. CD56neg NK cells, classically identified as CD56negCD16+, are very scarce in the peripheral blood of healthy people but they expand in some pathological conditions. However, studies on CD56neg NK cells had revealed different results regarding the phenotype and functionality. This could be due to, among others, the unstable expression of CD16, which hinders CD56neg NK cells’ proper identification. Hence, we aim to determine an alternative surface marker to CD16 to better identify CD56neg NK cells. We have found that NKp80 is superior to CD16. Furthermore, we found differences between the functionality of CD56negNKp80+ and CD56negCD16+, suggesting that the effector functions of CD56neg NK cells are not as diminished as previously thought. We proposed NKp80 as a noteworthy marker to identify and accurately re-characterize human CD56neg NK cells., Graphical Abstract, Highlights • NKp80 is a more precise marker than CD16 in order to identify CD56neg NK cells • CD16, but no NKp80, is downmodulated after cryopreservation and cell activation • CD56neg NK cells effector functions are not as diminished as previously described, Biological Sciences; Immunology

Lymphocytes proliferate in response to several stimuli. In many situations, a rapid lymphocyte expansion, or the identification of a slow dividing cell subpopulation may be of great interest. Thus, it is necessary to perform reliable assays to study and compare lymphocyte subsets proliferation. For this purpose, carboxifluorescein diacetate succinimidyl ester (CFSE) dilution assay has been stablished as a very useful tool that provides cumulative information about cell proliferation. Unlike other techniques that measure a static parameter of a specific time-point, CFSE staining allows to distinguish between subsequent cell divisions. Here, we show a simple protocol to study human T and NK cell proliferation with CFSE dilution assay by flow cytometry.

TGFβ in the tumor microenvironment diminishes natural killer (NK) cell–mediated anti-disialoganglioside (anti-GD2) mAb elimination of neuroblastoma cells. Consequently, blockade of TGFβ signaling with galunisertib in combination with the anti-GD2 mAb dinutuximab plus adoptively transferred NK cells is a promising tool for the treatment of neuroblastoma. Clin Cancer Res; 23(3); 615–7. ©2016 AACR. See related article by Tran et al., p. 804

Summary Although scarce in the peripheral blood of healthy people, CD56neg NK cells are known to be expanded in some pathological conditions. However, studies on CD56neg NK cells had revealed contradictions, probably due to the lack of a specific NK cell surface marker that helps to identify this subset. This protocol details the step-by-step procedure for the identification and functional analysis of CD56neg NK cells, providing an improved gating strategy for the selection of this intriguing population. For complete details on the use and execution of this protocol, please refer to Orrantia et al. (2020) .

Natural killer (NK) cells are cytotoxic lymphocytes that are able to kill tumor cells without prior sensitization. It has been shown that NK cells play a pivotal role in a variety of cancers, highlighting their relevance in tumor immunosurveillance. NK cell infiltration has been reported in renal cell carcinoma (RCC), the most frequent kidney cancer in adults, and their presence has been associated with patients’ survival. However, the role of NK cells in this disease is not yet fully understood. In this review, we summarize the biology of NK cells and the mechanisms through which they are able to recognize and kill tumor cells. Furthermore, we discuss the role that NK cells play in renal cell carcinoma, and review current strategies that are being used to boost and exploit their cytotoxic capabilities.

The CD300 molecules constitute an evolutionarily significant family of receptors that are expressed on myeloid and lymphoid cells, but also on other cell types, such as tuft cells. Many of the CD300 receptors have been shown to recognize lipids, e.g. phosphatidylserine and phosphatidylethanolamine. Over the past couple of years, accumulating evidence has shown that this family of receptors is involved in the pathogenesis of many diseases. Specifically, CD300 molecules participate in the mechanisms that viruses employ to develop immune evasion strategies and to infect host cells. The participation of CD300 molecules in viral infection includes both lipid dependent and independent mechanisms, as for example in infections with dengue virus (DENV) and murine norovirus (MNV), respectively. CD300 receptors are also involved in viral escape mechanisms, for instance inhibiting NK cell-mediated cytotoxicity against infected cells. Moreover, it is becoming increasingly recognized that the expression of CD300 receptors is altered during viral diseases. Here, we review the involvement of human and murine CD300 molecules in viral binding and entry and in cellular responses to viruses, which highlights the potential of CD300 molecules in the search of new biomarkers for various stages of infection and therapeutic targets for the treatment of viral infections.

The CD300a inhibitory receptor belongs to the CD300 family of cell surface molecules that regulate a diverse array of immune cell processes. The inhibitory signal of CD300a depends on the phosphorylation of tyrosine residues embedded in ITIMs of the cytoplasmic tail. CD300a is broadly expressed on myeloid and lymphoid cells, and its expression is differentially regulated depending on the cell type. The finding that CD300a recognizes phosphatidylserine and phosphatidylethanolamine, two aminophospholipids exposed on the outer leaflet of dead and activated cells, has shed new light on its role in the modulation of immune functions and in its participation in the host response to several diseases states, such as infectious diseases, cancer, allergy, and chronic inflammatory diseases. This review summarizes the literature on CD300a expression, regulation, signaling pathways, and ligand interaction, as well as its role in fine tuning immune cell functions and its clinical relevance.

Background Basophils express high-affinity IgE receptors (FceRI), which play an essential role in allergic diseases. It is important to characterize new cell-surface receptors that modulate IgE-mediated basophil activation threshold to design promising immunomodulatory therapies. Objectives We sought to analyze the expression of CD300 receptors on human basophils and their implication in IgE-mediated basophil activation processes. Methods Blood samples from healthy subjects and patients with cow's milk allergy were collected through the Basque Biobank under an institutional review board–approved protocol. PBMCs were obtained by means of density centrifugation, basophils were purified with a specific isolation kit, and phenotypic and functional studies were performed by using flow cytometry. Results We demonstrate that basophils express the activating receptor CD300c, which is specifically upregulated in response to IL-3. CD300c works as a costimulatory molecule during IgE-mediated basophil activation, as shown by a significant increase in degranulation and cytokine production when basophils are activated in the presence of CD300c cross-linking compared with activation through the IgE/FceRI axis alone. Coligation of FceRI and CD300c increased intracellular calcium mobilization and phosphorylation of signaling intermediates evoked only by FceRI ligation. We show that the natural ligands of CD300c, phosphatidylserine and phosphatidylethanolamine, modulate IgE-mediated basophil activation. Furthermore, we have observed that CD300c expression in children with cow's milk allergy is increased compared with that in healthy control subjects and that the intensity of expression correlates with the severity of the hypersensitivity symptoms. Conclusion CD300c could be considered a biomarker and therapeutic target in patients with IgE-mediated allergic diseases because it seems to be involved in the modulation of IgE-mediated basophil activation.

A modified vaccinia Ankara-based HIV-1 vaccine clade B (MVA-B) has been tested for safety and immunogenicity in low-risk human immunodeficiency virus (HIV)-uninfected individuals and as a therapeutic vaccine in HIV-1-infected individuals on combined antiretroviral therapy (cART). As a therapeutic vaccine, MVA-B was safe and broadly immunogenic; however, patients still showed a viral rebound upon treatment interruption. Monocytes are an important part of the viral reservoir and several studies suggest that they are partly responsible for the chronic inflammation observed in cART-treated HIV-infected people. The CD300 family of receptors has an important role in several diseases, including viral infections. Monocytes express CD300a, c, e, and f molecules and lipopolysaccharide (LPS) and other stimuli regulate their expression. However, the expression and function of CD300 receptors on monocytes in HIV infection is still unknown. In this work, we investigated for the first time the expression of CD300 molecules and the cytokine production in response to LPS on monocytes from HIV-1-infected patients before and after vaccination with MVA-B. Our results showed that CD300 receptors expression on monocytes from HIV-1-infected patients correlates with markers of HIV infection progression and immune inflammation. Specifically, we observed a positive correlation between the expression of CD300e and CD300f receptors on monocytes with the number of CD4+ T cells of HIV-1-infected patients before vaccination. We also saw a positive correlation between the expression of the inhibitory receptor CD300f and the expression of CD163 on monocytes from HIV-1-infected individuals before and after vaccination. In addition, monocytes exhibited a higher cytokine production in response to LPS after vaccination, almost at the same levels of monocytes from healthy donors. Furthermore, we also described a correlation in the expression of CD300e and CD300f receptors with TNF-α production in response to LPS, only in monocytes of HIV-1-infected patients before vaccination. Altogether, our results describe the impact of HIV-1 and of the MVA-B vaccine in cytokine production and monocytes phenotype.

Neonates are more susceptible to infections than adults. This susceptibility is thought to reflect neonates’ qualitative and quantitative defects in the adaptive and innate immune responses. Differential expression of cell surface receptors may result in altered thresholds of neonatal immune cell activation. We determined whether the expression and function of the lipid-binding CD300 family of receptors are different on neonatal immune cells compared to adult immune cells. A multiparametric flow cytometry analysis was performed to determine the expression of CD300 receptors on adult peripheral blood mononuclear cells and neonatal cord blood mononuclear cells. The expression of the CD300a inhibitory receptor was significantly reduced on cells from the newborn adaptive immune system, and neonatal antigen presenting cells exhibited a different CD300 receptors expression pattern. We also found differential LPS-mediated regulation of CD300 receptors expression on adult monocytes compared to cord blood monocytes, and that CD300c and CD300e-mediated activation was quantitatively different in neonatal monocytes. This is the first complete study examining the expression of CD300 receptors on human neonatal immune cells compared with adult immune cells. Significant differences in the expression and function of CD300 receptors may help to explain the peculiarities and distinctness of the neonatal immune responses.