CD69-mediated pathway of lymphocyte activation: anti-CD69 monoclonal antibodies trigger the cytolytic activity of different lymphoid effector cells with the exception of cytolytic T lymphocytes expressing T cell receptor alpha/beta

CD69 Signaling in Eosinophils Induces IL-10 Production and Apoptosis via the Erk1/2 and JNK Pathways, Respectively

INTRODUCTION

Eosinophils contribute to the pathogenesis of allergic diseases, including asthma, allergic rhinitis, and atopic dermatitis. We previously reported that human tissue eosinophils have high CD69 expression compared to blood eosinophils, and its expression is correlated with disease severity and the number of infiltrated eosinophils. However, biological CD69 signaling activity in eosinophils remains unclear.

METHODS

CD69 expression on lung tissue eosinophils obtained from mice with ovalbumin-induced asthma was measured using flow cytometry. CD69 crosslinking was performed on eosinophils purified from the spleen of IL-5 transgenic mice to investigate CD69 signaling and its function in eosinophils. Then, qPCR, Western blot, enzyme-linked immunosorbent assay, and survival assay results were analyzed.

RESULTS

Surface CD69 expression on lung tissue eosinophils in the asthma mice model was 2.91% ± 0.76%, whereas no expression was detected in the healthy group. CD69-expressed eosinophils intrinsically have an upregulation of IL-10 mRNA expression. Moreover, CD69 crosslinking induced further pronounced IL-10 production and apoptosis; these responses were mediated via the Erk1/2 and JNK pathways, respectively.

CONCLUSIONS

Our results suggested that CD69+ eosinophils play an immunoregulator role in type 2 inflammation, whereas activated tissue eosinophils contribute to the pathogenesis of asthma.

Interferon-epsilon is a novel regulator of NK cell responses in the uterus

The uterus is a unique mucosal site where immune responses are balanced to be permissive of a fetus, yet protective against infections. Regulation of natural killer (NK) cell responses in the uterus during infection is critical, yet no studies have identified uterine-specific factors that control NK cell responses in this immune-privileged site. We show that the constitutive expression of IFNε in the uterus plays a crucial role in promoting the accumulation, activation, and IFNγ production of NK cells in uterine tissue during Chlamydia infection. Uterine epithelial IFNε primes NK cell responses indirectly by increasing IL-15 production by local immune cells and directly by promoting the accumulation of a pre-pro-like NK cell progenitor population and activation of NK cells in the uterus. These findings demonstrate the unique features of this uterine-specific type I IFN and the mechanisms that underpin its major role in orchestrating innate immune cell protection against uterine infection.

Single-cell transcriptomics reveal different maturation stages and sublineage commitment of human thymic invariant natural killer T cells

Invariant natural killer T cells are a rare, heterogeneous T-cell subset with cytotoxic and immunomodulatory properties. During thymic development, murine invariant natural killer T cells go through different maturation stages differentiating into distinct sublineages, namely, invariant natural killer T1, 2, and 17 cells. Recent reports indicate that invariant natural killer T2 cells display immature properties and give rise to other subsets, whereas invariant natural killer T1 cells seem to be terminally differentiated. Whether human invariant natural killer T cells follow a similar differentiation model is still unknown. To define the maturation stages and assess the sublineage commitment of human invariant natural killer T cells during thymic development, in this study, we performed single-cell RNA sequencing analysis on human Vα24+Vβ11+ invariant natural killer T cells isolated from thymocytes. We show that these invariant natural killer T cells displayed heterogeneity, and our unsupervised analysis identified 5 clusters representing different maturation stages, from an immature profile with high expression of genes important for invariant natural killer T cell development and proliferation to a mature, fully differentiated profile with high levels of cytotoxic effector molecules. Evaluation of expression of sublineage-defining gene sets revealed mainly cells with an invariant natural killer T2 signature in the most immature cluster, whereas the more differentiated ones displayed an invariant natural killer T1 signature. Combined analysis with a publicly available single-cell RNA sequencing data set of human invariant natural killer T cells from peripheral blood suggested that the 2 main subsets exist both in thymus and in the periphery, while a third more immature one was restricted to the thymus. Our data point to the existence of different maturation stages of human thymic invariant natural killer T cells and provide evidence for sublineage commitment of invariant natural killer T cells in the human thymus.

Differential Immune-Modulating Activities of Cell Walls and Secreted Metabolites from Probiotic Bacillus coagulans JBI-YZ6.3 under Normal versus Inflamed Culture Conditions

Spore-forming probiotic bacteria, including Bacillus coagulans, are resilient and produce a variety of beneficial metabolites. We evaluated the immune-modulating effects of the novel probiotic strain Bacillus coagulans JBI-YZ6.3, where the germinated spores, metabolite fraction, and cell wall fraction were tested in parallel using human peripheral blood mononuclear cell cultures under both normal and lipopolysaccharide-induced inflamed culture conditions. The expression of CD25 and CD69 activation markers was evaluated via flow cytometry. Supernatants were tested for cytokines, interferons, chemokines, and growth factors using Luminex arrays. The germinated spores were highly immunogenic; both the cell wall and metabolite fractions contributed significantly. Under normal culture conditions, increased levels of immune activation were observed as increased expressions of CD25 and CD69 relative to natural killer cells, suggesting an increased ability to attack virus-infected target cells. On monocytes, a complex effect was observed, where the expression of CD25 increased under normal conditions but decreased under inflamed conditions. This, in combination with increased interleukin-10 (IL-10) and decreased monocyte chemoattractant protein-1 (MCP-1) production under inflamed conditions, points to anti-inflammatory effects. The production of the stem cell-related growth factor granulocyte colony-stimulating Factor (G-CSF) was enhanced. Further research is warranted to characterize the composition of the postbiotic metabolite fraction and document the characteristics of immunomodulating agents secreted by this probiotic strain.

Rapid increase in immune surveillance and expression of NKT and γδT cell activation markers after consuming a nutraceutical supplement containing Aloe vera gel, extracts of Poria cocos and rosemary. A randomized placebo-controlled cross-over trial

GOAL

To evaluate the acute impact of a nutraceutical blend on immune surveillance.

STUDY DESIGN

A randomized, double-blind, placebo-controlled, cross-over trial was conducted in 11 healthy subjects. Blood samples were taken immediately before and at 1, 2, and 3 hours after consuming placebo or 500 mg of UP360, which is a blend of botanicals from Aloe vera, Poria cocos, and rosemary (APR extract). Immunophenotyping and flow cytometry quantified numbers of monocytes, NK cells, NKT cells, CD8+ cytotoxic T cells, γδT cells, and total T cells, and expression of CD25 and CD69 activation markers. Plasma was tested for cytokines, chemokines, growth factors, and enzymatic activity of superoxide dismutase and catalase.

RESULTS

Compared to the placebo, consumption of APR extract triggered rapid increases in chemokine levels starting at 1 hour, including IP-10 (P<0.05) and MCP-1 (P<0.1), which peaked at 2 hours (P<0.01) and 3 hours (P<0.05), respectively. The stem cell-mobilizing growth factor G-CSF increased at 2 hours (P<0.05). Increased immune surveillance involved a transient effect for monocytes at 1 hour, followed by NKT cells, CD8+ cytotoxic T cells, and γδT cells at 2-3 hours. Increased immune cell alertness was seen at 1 hour by increased CD25 expression on monocytes (P<0.01), NKT cells (P<0.01), and T cells (P<0.05). NKT cells showed upregulation of CD69 at 2 hours (P<0.01). Increased enzymatic activity was seen at 2 hours for the antioxidant enzymes superoxide dismutase (P<0.05) and catalase (P<0.01).

CONCLUSION

Consumption of APR extract triggered acute changes to chemokine levels. In addition, immune alertness was increased via the expression of activation markers on multiple types of innate immune cells, followed by increased immune surveillance and antioxidant protection. This suggests a beneficial enhancement of natural immune surveillance, likely via a combination of gut-mediated cytokine release and vagus nerve communication, in combination with cellular protection from oxidative stress.

Advances in Immunomodulatory Mechanisms of Mesenchymal Stem Cells-Derived Exosome on Immune Cells in Scar Formation

Pathological scars are the result of over-repair and excessive tissue proliferation of the skin injury. It may cause serious dysfunction, resulting in psychological and physiological burdens on the patients. Currently, mesenchymal stem cells-derived exosomes (MSC-Exo) displayed a promising therapeutic effect on wound repair and scar attenuation. But the regulatory mechanisms are opinions vary. In view of inflammation has long been proven as the initial factor of wound healing and scarring, and the unique immunomodulation mechanism of MSC-Exo, the utilization of MSC-Exo may be promising therapeutic for pathological scars. However, different immune cells function differently during wound repair and scar formation. The immunoregulatory mechanism of MSC-Exo would differ among different immune cells and molecules. Herein, this review gave a comprehensive summary of MSC-Exo immunomodulating different immune cells in wound healing and scar formation to provide basic theoretical references and therapeutic exploration of inflammatory wound healing and pathological scars.

Unraveling CD69 signaling pathways, ligands and laterally associated molecules

CD69 is an early leukocyte activation marker involved in the regulation of the immune response. Initial in vitro studies evaluated its function using monoclonal antibodies until knock-out mice were developed. Subsequently, four ligands for CD69 have been identified, namely galectin-1, S100A8/S100A9 complex, myosin light chains 9 and 12, and oxidized low-density lipoproteins. In addition, several molecules are laterally associated with and regulated by CD69, including calreticulin and two transmembrane receptors, sphingosine-1-phosphate receptor (S1P1) and the heterodimeric amino acid transporter complex SLC7A5-SLC3A2 (LAT1-CD98). Recently, CD69 engagement has been shown to induce the expression of the immunoregulatory receptor programmed cell death-1 (PD-1) in T cells. The molecular signaling induced by CD69 has been explored in different scenarios and cell types. This review provides a perspective on the molecular pathways, ligands and cellular functions known to be regulated by CD69.

T cell kinetics reveal expansion of distinct lung T cell subsets in acute versus in resolved influenza virus infection

Influenza virus infection is restricted to airway-associated tissues and elicits both cellular and humoral responses ultimately resulting in generation of memory cells able to initiate a rapid immune response against re-infections. Resident memory T cells confer protection at the site of infection where lung-resident memory T cells are important for protecting the host against homologous and heterologous influenza virus infections. Mapping kinetics of local and systemic T cell memory formation is needed to better understand the role different T cells have in viral control and protection. After infecting BALB/c mice with influenza virus strain A/Puerto Rico/8/1934 H1N1 the main proportion of activated T cells and B cells expressing the early activation marker CD69 was detected in lungs and lung-draining mediastinal lymph nodes. Increased frequencies of activated cells were also observed in the peripheral lymphoid organs spleen, inguinal lymph nodes and mesenteric lymph nodes. Likewise, antigen-specific T cells were most abundant in lungs and mediastinal lymph nodes but present in all organs studied. CD8+CD103-CD49a+ lung-resident T cells expanded simultaneously with timing of viral clearance whereas CD8+CD103+CD49a+ lung-resident T cells was the most abundant subset after resolution of infection and antigen-specific, lung-resident T cells were detected up to seven months after infection. In conclusion, the results in this detailed kinetic study demonstrate that influenza virus infection elicits adaptive immune responses mainly in respiratory tract-associated tissues and that distinct subsets of lung-resident T cells expand at different time points during infection. These findings contribute to the understanding of the adaptive immune response locally and systemically following influenza virus infection and call for further studies on the roles of the lung-resident T cell subsets.

Exploring the Utility of NK Cells in COVID-19

Coronavirus disease 2019 (COVID-19) can manifest as acute respiratory distress syndrome and is associated with substantial morbidity and mortality. Extensive data now indicate that immune responses to SARS-CoV-2 infection determine the COVID-19 disease course. A wide range of immunomodulatory agents have been tested for the treatment of COVID-19. Natural killer (NK) cells play an important role in antiviral innate immunity, and anti-SARS-CoV-2 activity and antifibrotic activity are particularly critical for COVID-19 control. Notably, SARS-CoV-2 clearance rate, antibody response, and disease progression in COVID-19 correlate with NK cell status, and NK cell dysfunction is linked with increased SARS-CoV-2 susceptibility. Thus, NK cells function as the key element in the switch from effective to harmful immune responses in COVID-19. However, dysregulation of NK cells has been observed in COVID-19 patients, exhibiting depletion and dysfunction, which correlate with COVID-19 severity; this dysregulation perhaps contributes to disease progression. Given these findings, NK-cell-based therapies with anti-SARS-CoV-2 activity, antifibrotic activity, and strong safety profiles for cancers may encourage the rapid application of functional NK cells as a potential therapeutic strategy to eliminate SARS-CoV-2-infected cells at an early stage, facilitate immune–immune cell interactions, and favor inflammatory processes that prevent and/or reverse over-inflammation and inhibit fibrosis progression, thereby helping in the fight against COVID-19. However, our understanding of the role of NK cells in COVID-19 remains incomplete, and further research on the involvement of NK cells in the pathogenesis of COVID-19 is needed. The rationale of NK-cell-based therapies for COVID-19 has to be based on the timing of therapeutic interventions and disease severity, which may be determined by the balance between beneficial antiviral and potential detrimental pathologic actions. NK cells would be more effective early in SARS-CoV-2 infection and prevent the progression of COVID-19. Immunomodulation by NK cells towards regulatory functions could be useful as an adjunct therapy to prevent the progression of COVID-19.

Highly Multiplexed Image Analysis of Intestinal Tissue Sections in Patients With Inflammatory Bowel Disease

BACKGROUND & AIMS

Significant progress has been made since the first report of inflammatory bowel disease (IBD) in 1859, after decades of research that have contributed to the understanding of the genetic and environmental factors involved in IBD pathogenesis. Today, a range of treatments is available for directed therapy, mostly targeting the overactive immune response. However, the mechanisms by which the immune system contributes to disease pathogenesis and progression are not fully understood. One challenge hindering IBD research is the heterogeneous nature of the disease and the lack of understanding of how immune cells interact with one another in the gut mucosa. Introduction of a technology that enables expansive characterization of the inflammatory environment of human IBD tissues may address this gap in knowledge.

METHODS

We used the imaging mass cytometry platform to perform highly multiplex image analysis of IBD and healthy deidentified intestine sections (6 Crohn's disease compared to 6 control ileum; 6 ulcerative colitis compared to 6 control colon). The acquired images were graded for inflammation severity by analysis of adjacent H&E tissue sections. We assigned more than 300,000 cells to unique cell types and performed analyses of tissue integrity, epithelial activity, and immune cell composition.

RESULTS

The intestinal epithelia of patients with IBD exhibited increased proliferation rates and expression of HLA-DR compared to control tissues, and both features were positively correlated with the severity of inflammation. The neighborhood analysis determined enrichment of regulatory T cell interactions with CD68⁺ macrophages, CD4⁺ T cells, and plasma cells in both forms of IBD, whereas activated lysozyme C⁺ macrophages were preferred regulatory T cell neighbors in Crohn's disease but not ulcerative colitis.

CONCLUSIONS

Altogether, our study shows the power of imaging mass cytometry and its ability to both quantify immune cell types and characterize their spatial interactions within the inflammatory environment by a single analysis platform.

Extracellular Vesicle Surface Signatures in IPF Patients: A Multiplex Bead-Based Flow Cytometry Approach

Background: Extracellular vesicles (EVs) are secreted by cells from their membrane within circulation and body fluids. Knowledge of the involvement of EVs in pathogenesis of lung diseases is increasing. The present study aimed to evaluate the expression of exosomal surface epitopes in a cohort of idiopathic pulmonary fibrosis (IPF) patients followed in two Italian Referral Centres for Interstitial Lung Diseases, comparing them with a group of healthy volunteers. Materials and Methods: Ninety IPF patients (median age and interquartile range (IQR) 71 (66–75) years; 69 males) were selected retrospectively. Blood samples were obtained from patients before starting antifibrotic therapy. A MACSPlex Exosome Kit, human, (Miltenyi Biotec, Bergisch-Gladbach, Germany), to detect 37 exosomal surface epitopes, was used. Results: CD19, CD69, CD8, and CD86 were significantly higher in IPF patients than in controls (p = 0.0023, p = 0.0471, p = 0.0082, and p = 0.0143, respectively). CD42a was lower in IPF subjects than in controls (p = 0.0153), while CD209, Cd133/1, MCSP, and ROR1 were higher in IPF patients than in controls (p = 0.0007, p = 0.0050, p = 0.0139, and p = 0.0335, respectively). Kaplan-Meier survival analysis for IPF patients: for median values and a cut-off of 0.48 for CD25, the two subgroups showed a significant difference in survival rate (p = 0.0243, hazard ratio: 0.52 (95%CI 0.29–0.92); the same was true for CD8 (cut-off 1.53, p = 0.0309, hazard ratio: 1.39 (95%CI 0.75–2.53). Conclusion: Our multicenter study showed for the first time the expression of surface epitopes on EVs from IPF patients, providing interesting data on the communication signatures/exosomal profile in serum from IPF patients and new insights into the pathogenesis of the disease and a promising reliability in predicting mid-term survival of IPF patients.

Extensive activation, tissue trafficking, turnover and functional impairment of NK cells in COVID-19 patients at disease onset associates with subsequent disease severity

The SARS-CoV-2 infection causes severe respiratory involvement (COVID-19) in 5-20% of patients through initial immune derangement, followed by intense cytokine production and vascular leakage. Evidence of immune involvement point to the participation of T, B, and NK cells in the lack of control of virus replication leading to COVID-19. NK cells contribute to early phases of virus control and to the regulation of adaptive responses. The precise mechanism of NK cell dysregulation is poorly understood, with little information on tissue margination or turnover. We investigated these aspects by multiparameter flow cytometry in a cohort of 28 patients hospitalized with early COVID-19. Relevant decreases in CD56brightCD16+/- NK subsets were detected, with a shift of circulating NK cells toward more mature CD56dimCD16+KIR+NKG2A+ and "memory" KIR+CD57+CD85j+ cells with increased inhibitory NKG2A and KIR molecules. Impaired cytotoxicity and IFN-γ production were associated with conserved expression of natural cytotoxicity receptors and perforin. Moreover, intense NK cell activation with increased HLA-DR and CD69 expression was associated with the circulation of CD69+CD103+ CXCR6+ tissue-resident NK cells and of CD34+DNAM-1brightCXCR4+ inflammatory precursors to mature functional NK cells. Severe disease trajectories were directly associated with the proportion of CD34+DNAM-1brightCXCR4+ precursors and inversely associated with the proportion of NKG2D+ and of CD103+ NK cells. Intense NK cell activation and trafficking to and from tissues occurs early in COVID-19, and is associated with subsequent disease progression, providing an insight into the mechanism of clinical deterioration. Strategies to positively manipulate tissue-resident NK cell responses may provide advantages to future therapeutic and vaccine approaches.

The mycelium of the Trametes versicolor (Turkey tail) mushroom and its fermented substrate each show potent and complementary immune activating properties in vitro

BACKGROUND

The medicinal mushroom Trametes versicolor (Tv, Turkey Tail) is often prepared for consumption as a powder from the fungal mycelium and the fermented substrate on which it grew. The goal for this study was to evaluate the immune-modulating properties of the mycelium versus the fermented substrate, to document whether an important part of the immune-activating effects resides in the metabolically fermented substrate.

METHODS

Tv mycelium was cultured on rice flour. The mycelium and the fermented substrate were mechanically separated, dried, and milled. The initial substrate served as a control. Aqueous fractions were extracted and passed through 0.22-μm filters. The remaining solids were passed through homogenization spin columns without filtration. The aqueous and solid fractions of the initial substrate (IS), the fermented substrate (FS), and the Trametes versicolor mycelium (TvM) were tested for immune-activating and modulating activities on human peripheral blood mononuclear cell cultures, to examine expression of the CD69 activation marker on lymphocytes versus monocytes, and on the T, NKT, and NK lymphocyte subsets. Culture supernatants were tested for cytokines using Luminex arrays.

RESULTS

Both aqueous and solid fractions of TvM triggered robust induction of CD69 on lymphocytes and monocytes, whereas FS only triggered minor induction of CD69, and IS had no activating effect. The aqueous extract of TvM had stronger activating effects than the solid fraction. In contrast, the solid fraction of IS triggered a reduction in CD69, below levels on untreated cells. Both aqueous and solid fractions of FS triggered large and dose-dependent increases in immune-activating pro-inflammatory cytokines (IL-2, IL-6), anti-inflammatory cytokines Interleukin-1 receptor antagonist (IL-1ra) and Interleukin-10 (IL-10), anti-viral cytokines interferon-gamma (IFN-γ) and Macrophage Inflammatory Protein-alpha (MIP-1α), as well as Granulocyte-Colony Stimulating Factor (G-CSF) and Interleukin-8 (IL-8). TvM triggered more modest cytokine increases. The aqueous extract of IS showed no effects, whereas the solid fraction showed modest effects on induction of cytokines and growth factors.

CONCLUSION

The results demonstrated that the immune-activating bioactivity of a mycelial-based medicinal mushroom preparation is a combination of the mycelium itself (including insoluble beta-glucans, and also water-soluble components), and the highly bioactive, metabolically fermented substrate, not present in the initial substrate.

Particulate and solubilized β-glucan and non-β-glucan fractions of Euglena gracilis induce pro-and anti-inflammatory innate immune cell responses and exhibit antioxidant properties

Purpose

The purpose of this work was to determine the pro-and anti-inflammatory properties of the single-cell organism Euglena gracilis (EG) and various fractions of its whole biomass.

Methods

Heterotrophically grown EG was tested, along with its aqueous fraction (E-AQ), the intact linear β-glucan paramylon granules (PAR), and alkaline-solubilized paramylon. Peripheral blood mononuclear cell cultures were treated with the test products and analyzed for a variety of cellular responses. Immune cell activation was evaluated by flow cytometry detection of CD69 levels on CD3^-CD56⁺ NK cells, CD3⁺CD56⁺ NKT cells, and monocytes, and cytokines were analyzed from the cell culture supernatants. Antioxidant capacity was measured by Folin-Ciocalteu assay and cellular antioxidant protection and MTT assays.

Results

EG and E-AQ were the most effective in driving immune cell responses as measured by CD69 upregulation on NK and NKT cells and proinflammatory (tumor necrosis factor, IL-6, IL-1β) cytokine production. None of the test products effectively stimulated monocyte. EG and PAR inhibited reactive oxygen species under conditions of oxidative stress. E-AQ contained antioxidants capable of providing cellular antioxidant protection from oxidative damage and protection of mitochondrial function under inflammatory conditions.

Conclusion

The effects of EG on immune function are only partially attributable to the content of the β-glucan, paramylon. The regulation of additional cellular responses, such a reactive oxygen species production and resistance to oxidative stress, is likely mediated by currently unknown molecules found in the EG cell.

Novel Immunoregulatory Functions of IL-18, an Accomplice of TGF-β1

TGF-β1 is a pleiotropic factor exerting a strong regulatory role in several cell types, including immune cells. In NK cells it profoundly alters the surface expression of crucial activating and chemokine receptors. To understand which soluble signals might better contrast these effects, we cultured human NK cells in the presence of TGF-β1 and different innate and adaptive cytokines, generally referred as “immunostimulatory”. These included IL-2, IL-15, IL-21, IL-27, and IL-18. Unexpectedly, IL-18 strengthened rather than contrasting important TGF-β1-mediated functions. In particular, IL-18 further reduced the expression of CX₃CR1 and NKp30, leading to the virtual abrogation of the triggering capability of this activating receptor. Moreover, IL-18 further increased the expression of CXCR4. The IL-18-mediated additive effect on NKp30 and CXCR4 expression involved transcriptional regulation and activation of MEK/ERK and/or p38MAPK. A proteomic approach quantified both surface and intracellular proteins significantly modified in cytokine-treated NK cells, thus giving global information on the biological processes involving TGF-β1 and IL-18. Our data support the concept that IL-18 may have a different behavior depending on the type of soluble factors characterizing the microenvironment. In a TGF-β1 rich milieu such as tumors, it may contribute to the impairment of both NK cells recruitment and killing capability.

CD84 regulates PD-1/PD-L1 expression and function in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by clonal proliferation and progressive accumulation of mature B lymphocytes in the peripheral blood, lymphoid tissues, and bone marrow. CLL is characterized by profound immune defects leading to severe infectious complications. T cells are numerically, phenotypically, and functionally highly abnormal in CLL, with only limited ability to exert antitumor immune responses. Exhaustion of T cells has also been suggested to play an important role in antitumor responses. CLL-mediated T cell exhaustion is achieved by the aberrant expression of several inhibitory molecules on CLL cells and their microenvironment, prominently the programmed cell death ligand 1/programmed cell death 1 (PD-L1/PD-1) receptors. Previously, we showed that CD84, a member of the SLAM family of receptors, bridges between CLL cells and their microenvironment. In the current study, we followed CD84 regulation of T cell function. We showed that cell-cell interaction mediated through human and mouse CD84 upregulates PD-L1 expression on CLL cells and in their microenvironment and PD-1 expression on T cells. This resulted in suppression of T cell responses and activity in vitro and in vivo. Thus, our results demonstrate a role for CD84 in the regulation of immune checkpoints by leukemia cells and identify CD84 blockade as a therapeutic strategy to reverse tumor-induced immune suppression.

High neutrophil to lymphocyte ratio and decreased CD69+NK cells represent a phenotype of high risk in early-stage breast cancer patients

Purpose

Breast cancer (BC) is a highly heterogeneous disease presenting a broad range of clinical and molecular characteristics. In the past years, a growing body of evidence demonstrated that immune response plays a significant role in cancer outcome. However, immune prognostic markers are not completely validated in clinical practice in BC patients.

Materials and methods

With the aim to characterize immune features, several parameters were analyzed in peripheral blood at diagnosis of 85 nonmetastatic BC patients between April 2011 and July 2014.

Results

With a median follow-up of 38.6 months, peripheral blood analysis of BC patients (stages I, II, and III) showed that total lymphocyte and T lymphocyte counts were augmented in nonrelapsed patients. Also, a higher neutrophil-to-lymphocytes ratio was associated with prolonged disease-free survival. Natural killer cell receptor analysis revealed that early activation receptor CD69 was associated with a better outcome.

Conclusion

This preliminary evidence is in accordance with the concept of immune surveillance. We suggest an “immune phenotype” that provides relevant prognostic information in early-stage BC patients and which could be useful in the decision-making process.

Role of P-glycoprotein on CD69+CD4+ cells in the pathogenesis of proliferative lupus nephritis and non-responsiveness to immunosuppressive therapy

Introduction

P-glycoprotein (P-gp) expression on activated lymphocytes in systemic lupus erythematosus (SLE) plays a role in active efflux of intracellular drugs, resulting in drug resistance. The role of P-gp-expressing lymphocytes in the pathogenesis of SLE remains unclear. The aim of this study was to determine the importance of P-gp⁺CD4⁺ cells in organ manifestations in refractory SLE.

Methods

The proportion of P-gp⁺CD4⁺ cells was determined by flow cytometry in peripheral blood of patients with SLE (n=116) and healthy adults (n=10). Renal biopsy specimens were examined by immunohistochemistry for P-gp expression.

Results

CD69 is a marker of CD4 cell activation. The proportion of both P-gp-expressing CD4⁺ cells and CD69-expressing CD4⁺ cells in peripheral blood was higher in SLE than control. The proportion of P-gp⁺CD69⁺CD4⁺ cells correlated with Systemic Lupus Erythematosus Disease Activity Index and was higher in poor responders to corticosteroids. Furthermore, the proportion of P-gp⁺CD69⁺CD4⁺ cells was significantly higher in proliferative lupus nephritis (LN) with poor response to corticosteroids. The efficacy of immunosuppressive therapy depended on the regulation of the proportion of P-gp⁺CD69⁺CD4⁺ cells. Marked accumulation of P-gp⁺CD4⁺ cells in renal interstitial tissue and high proportion of peripheral P-gp⁺CD69⁺CD4⁺ cells were noted in patients with proliferative LN.

Conclusions

The results showed high proportion of P-gp⁺CD69⁺CD4⁺ cells in peripheral blood and their accumulation in renal tissue in patients with proliferative LN refractory to CS therapy, suggesting that P-gp expression on activated CD4⁺ T cells is a potentially useful marker for refractoriness to treatment and a novel target for treatment.

Inactivated probiotic Bacillus coagulans GBI-30 induces complex immune activating, anti-inflammatory, and regenerative markers in vitro

Objective

The aim of this study was to document the immune activating and anti-inflammatory effects of inactivated probiotic Bacillus coagulans GBI-30, 6086 (Staimune™) cells on human immune cells in vitro.

Methods

In vitro cultures of human peripheral blood mononuclear cells (PBMC) from healthy blood donors were treated with inactivated B. coagulans GBI-30, 6086 cells for 24 hours. After incubation, the PBMC were stained with fluorochrome-labeled monoclonal antibodies for CD3, CD56, and CD69 to monitor cellular activation by flow cytometry. The culture supernatants were tested for cytokine profile using a 27-plex Luminex array, including pro- and anti-inflammatory cytokines, chemokines, and growth factors.

Results

Inactivated B. coagulans GBI-30, 6086 cells induced the CD69 early activation marker on CD3⁺ CD56⁻ T lymphocytes, CD3⁺ CD56⁺ NKT cells, CD3⁻CD56⁺ NK cells, and also some cells within the CD3⁻CD56⁻ non-T non-NK cell subset. Culture supernatants showed robust increases in the immune-activating cytokines IL-1β, IL-6, IL-17A, and TNF-α. IFN-γ levels were increased, along with three chemokines, MCP-1, MIP-1α, and MIP-1β. The two anti-inflammatory cytokines IL-1ra and IL-10 showed increases, as well as the G-CSF growth factor involved in repair and stem cell biology. In contrast, GM-CSF levels showed a mild decrease, showing a highly selective growth factor response.

Conclusion

The inactivated B. coagulans GBI-30, 6086 cells activated human immune cells and altered the production of both immune activating and anti-inflammatory cytokines and chemokines. Of special importance is the novel demonstration of a selective upregulation of the G-CSF growth factor involved in postinjury and postinflammation repair and regeneration. This suggests that important immunogenic cell wall components, such as lipoteichoic acid, are undamaged after the inactivation and retain the complex beneficial biological activities previously demonstrated for the cell walls from live B. coagulans GBI-30, 6086 (GanedenBC30) probiotic bacteria.

Persistence of Activated and Adaptive-Like NK Cells in HIV+ Individuals despite 2 Years of Suppressive Combination Antiretroviral Therapy

Innate immune dysfunction persists in HIV⁺ individuals despite effective combination antiretroviral therapy (cART). We recently demonstrated that an adaptive-like CD56^dim NK cell population lacking the signal transducing protein FcRγ is expanded in HIV⁺ individuals. Here, we analyzed a cohort of HIV⁺ men who have sex with men (MSM, n = 20) at baseline and following 6, 12, and 24 months of cART and compared them with uninfected MSM (n = 15) to investigate the impact of cART on NK cell dysfunction. Proportions of NK cells expressing markers of early (CD69⁺) and late (HLA-DR⁺/CD38⁺) activation were elevated in cART-naïve HIV⁺ MSM (p = 0.004 and 0.015, respectively), as were FcRγ⁻ NK cells (p = 0.003). Using latent growth curve modeling, we show that cART did not reduce levels of FcRγ⁻ NK cells (p = 0.115) or activated HLA-DR⁺/CD38⁺ NK cells (p = 0.129) but did reduce T cell and monocyte activation (p < 0.001 for all). Proportions of FcRγ⁻ NK cells were not associated with NK cell, T cell, or monocyte activation, suggesting different factors drive CD56^dim FcRγ⁻ NK cell expansion and immune activation in HIV⁺ individuals. While proportions of activated CD69⁺ NK cells declined significantly on cART (p = 0.003), the rate was significantly slower than the decline of T cell and monocyte activation, indicating a reduced potency of cART against NK cell activation. Our findings indicate that 2 years of suppressive cART have no impact on CD56^dim FcRγ⁻ NK cell expansion and that NK cell activation persists after normalization of other immune parameters. This may have implications for the development of malignancies and co-morbidities in HIV⁺ individuals on cART.

T Cell Transcriptomes from Paroxysmal Nocturnal Hemoglobinuria Patients Reveal Novel Signaling Pathways

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired disorder originating from hematopoietic stem cells and is a life-threating disease characterized by intravascular hemolysis, bone marrow (BM) failure, and venous thrombosis. The etiology of PNH is a somatic mutation in the phosphatidylinositol glycan class A gene (PIG-A) on the X chromosome, which blocks synthesis of the glycolipid moiety and causes deficiency in GPI-anchored proteins. PNH is closely related to aplastic anemia, in which T cells mediate destruction of BM. To identify aberrant molecular mechanisms involved in immune targeting of hematopoietic stem cells in BM, we applied RNA-seq to examine the transcriptome of T cell subsets (CD4⁺ naive, CD4⁺ memory, CD8⁺ naive, and CD8⁺ memory) from PNH patients and healthy control subjects. Differentially expressed gene analysis in four different T cell subsets from PNH and healthy control subjects showed distinct transcriptional profiles, depending on the T cell subsets. By pathway analysis, we identified novel signaling pathways in T cell subsets from PNH, including increased gene expression involved in TNFR, IGF1, NOTCH, AP-1, and ATF2 pathways. Dysregulation of several candidate genes (JUN, TNFAIP3, TOB1, GIMAP4, GIMAP6, TRMT112, NR4A2, CD69, and TNFSF8) was validated by quantitative real-time RT-PCR and flow cytometry. We have demonstrated molecular signatures associated with positive and negative regulators in T cells, suggesting novel pathophysiologic mechanisms in PNH. These pathways may be targets for new strategies to modulate T cell immune responses in BM failure.

Decrease of CD69 levels on TCR Vα7.2+CD4+ innate-like lymphocytes is associated with impaired cytotoxic functions in chronic hepatitis B virus-infected patients

Hepatitis B virus (HBV) infection is a major cause of chronic liver disease that may progress to liver cirrhosis and hepatocellular carcinoma. Host immune responses represent the key determinants of HBV clearance or persistence. Here, we investigated the role of the early activation marker, CD69 and effector cytokines, granzyme B (GrB) and IFN-γ in the exhaustion of innate-like TCR Vα7.2⁺CD4⁺T cells, in 15 individuals with chronic HBV (CHB) infection where six were HBV DNA⁺ and nine were HBV DNA^-. The percentage of cytokine-producing T cells and MAIT cells were significantly perturbed in HBV patients relative to healthy controls (HCs). The intracellular expression of GrB and IFN-γ was significantly reduced in MAIT cells derived from HBV-infected patients as compared to HCs, and the levels correlated with the percentage and levels [mean fluorescence intensity (MFI)] of CD69 expression. The total expression of CD69 (iMFI) was lower in CHB patients as compared to HCs. The frequency of CD69⁺ cells correlated with the levels of cytokine expression (MFI), particularly in CHB patients as compared to HCs. In summary, the polyfunctionality of peripheral T cells was significantly reduced among CHB patients, especially in the TCR Vα7.2⁺CD4⁺T cells, and the levels of cytokine expression correlated with functional cytokine levels.

Effect of a high and low dose of caffeine on human lymphocyte activation in response to antigen stimulation

This study investigated the effect of caffeine on antigen-stimulated lymphocyte activation. Six males rested for 3.5 h after ingesting 0 (PLA), 2, or 6 (6CAF) mg·kg(-1) body mass of caffeine. The number of antigen-stimulated NK CD69(+) cells increased in 6CAF at 1 h compared with PLA (P = 0.021). Caffeine did not influence the number of antigen-stimulated CD69(+) T cells or the geometric mean fluorescence intensity expression of CD69 on antigen-stimulated lymphocytes, suggesting caffeine has little effect on antigen-stimulated lymphocyte activation.

Innate Immune Activity Correlates with CD4 T Cell-Associated HIV-1 DNA Decline during Latency-Reversing Treatment with Panobinostat

The pharmaceutical reactivation of dormant HIV-1 proviruses by histone deacetylase inhibitors (HDACi) represents a possible strategy to reduce the reservoir of HIV-1-infected cells in individuals treated with suppressive combination antiretroviral therapy (cART). However, the effects of such latency-reversing agents on the viral reservoir size are likely to be influenced by host immune responses. Here, we analyzed the immune factors associated with changes in proviral HIV-1 DNA levels during treatment with the potent HDACi panobinostat in a human clinical trial involving 15 cART-treated HIV-1-infected patients. We observed that the magnitude, breadth, and cytokine secretion profile of HIV-1-specific CD8 T cell responses were unrelated to changes in HIV-1 DNA levels in CD4 T cells during panobinostat treatment. In contrast, the proportions of CD3(-) CD56(+) total NK cells and CD16(+) CD56(dim) NK cells were inversely correlated with HIV-1 DNA levels throughout the study, and changes in HIV-1 DNA levels during panobinostat treatment were negatively associated with the corresponding changes in CD69(+) NK cells. Decreasing levels of HIV-1 DNA during latency-reversing treatment were also related to the proportions of plasmacytoid dendritic cells, to distinct expression patterns of interferon-stimulated genes, and to the expression of the IL28B CC genotype. Together, these data suggest that innate immune activity can critically modulate the effects of latency-reversing agents on the viral reservoir and may represent a target for future immunotherapeutic interventions in HIV-1 eradication studies.

IMPORTANCE

Currently available antiretroviral drugs are highly effective in suppressing HIV-1 replication, but the virus persists, despite treatment, in a latent form that does not actively express HIV-1 gene products. One approach to eliminate these cells, colloquially termed the "shock-and-kill" strategy, focuses on the use of latency-reversing agents that induce active viral gene expression in latently infected cells, followed by immune-mediated killing. Panobinostat, a histone deacetylase inhibitor, demonstrated potent activities in reversing HIV-1 latency in a recent pilot clinical trial and reduced HIV-1 DNA levels in a subset of patients. Interestingly, we found that innate immune factors, such as natural killer cells, plasmacytoid dendritic cells, and the expression patterns of interferon-stimulated genes, were most closely linked to a decline in the HIV-1 DNA level during treatment with panobinostat. These data suggest that innate immune activity may play an important role in reducing the residual reservoir of HIV-1-infected cells.

In vivo administration of the frog skin peptide frenatin 2.1S induces immunostimulatory phenotypes of mouse mononuclear cells

Host-defense peptides secreted by epithelial cells exhibit cytotoxic and immunoregulatory effects in order to protect the organism against invading microorganisms. Antimicrobial peptides derived from frog skin display both immunostimulatory and immunosuppressive actions as demonstrated by in vitro cytokine production by macrophages. Frenatin 2.1S, first isolated from skin secretions of the frog, Sphaenorhynchus lacteus (Hylidae), enhances the in vitro production of pro-inflammatory IL-1β, TNF-α and IL-23 by mouse peritoneal cells. In order to test whether the immunostimulatory action of frenatin 2.1S may be reproduced in vivo, effects of intraperitoneal injections of this peptide on mononuclear cells in the peritoneum and spleen were determined 24h after administration. The data indicate that frenatin 2.1S enhances the activation state and homing capacity of Th1 type lymphocytes and NKT cells in the mouse peritoneal cavity, as evaluated by increased expression of early activation marker CD69 among T and NKT cells and chemokine receptor CXCR3 among T cells. Frenatin 2.1S significantly increases the percentage of (F4/80(+)CD11c(+)CD206(+)) pro-inflammatory M1 macrophages and enhances the expression of MHC class II molecules on F4/80(+)CD11c(+) macrophages in the mouse peritoneal cavity. Additionally, injection of frenatin 2.1S, in the presence or absence of lipopolysaccharide, increases the percentage of peritoneal B cells of the (CD19(+)CD11b(+)CD5(+)) B1a phenotype thus contributing to an inflammatory milieu. We suggest that the immunostimulatory effect of frenatin 2.1S may have therapeutic relevance in disease states, such as certain types of cancer, in which an enhanced inflammatory response may be beneficial.

Mature resting Ly6C(high) natural killer cells can be reactivated by IL-15

Mature NK cells are heterogeneous as to their expression levels of cell surface molecules. However, the functional differences and physiological roles of each NK-cell subset are not fully understood. In this study, we report that based on the Ly6C expression levels, mature C57BL/6 murine NK cells can be subdivided into Ly6C(low) and Ly6C(high) subsets. Ly6C(high) NK cells are in an inert state as evidenced by the production of lower levels of IFN-γ and granzyme B, and they exhibit poorer proliferative potential than Ly6C(low) NK cells. In addition, adoptive transfer experiments revealed that Ly6C(high) NK cells are derived from Ly6C(low) NK cells in the steady state. These results strongly suggest that Ly6C(high) NK cells are resting cells in the steady state. However, in vitro, Ly6C(high) NK cells become Ly6C(low) NK cells with strong effector functions upon stimulation with IL-15. Moreover, Ly6C(high) NK cells also revert to Ly6C(low) NK cells in vivo upon injection of the IL-15 inducers polyI:C and CpG. Taken together, these results demonstrate the plasticity of mature NK cells and suggest that Ly6C(high) NK cells are a reservoir of potential NK cells that allow effective and strong response to infections.

Structural basis for recognition of cellular and viral ligands by NK cell receptors

Natural killer (NK) cells are key components of innate immune responses to tumors and viral infections. NK cell function is regulated by NK cell receptors that recognize both cellular and viral ligands, including major histocompatibility complex (MHC), MHC-like, and non-MHC molecules. These receptors include Ly49s, killer immunoglobulin-like receptors, leukocyte immunoglobulin-like receptors, and NKG2A/CD94, which bind MHC class I (MHC-I) molecules, and NKG2D, which binds MHC-I paralogs such as the stress-induced proteins MICA and ULBP. In addition, certain viruses have evolved MHC-like immunoevasins, such as UL18 and m157 from cytomegalovirus, that act as decoy ligands for NK receptors. A growing number of NK receptor–ligand interaction pairs involving non-MHC molecules have also been identified, including NKp30–B7-H6, killer cell lectin-like receptor G1–cadherin, and NKp80–AICL. Here, we describe crystal structures determined to date of NK cell receptors bound to MHC, MHC-related, and non-MHC ligands. Collectively, these structures reveal the diverse solutions that NK receptors have developed to recognize these molecules, thereby enabling the regulation of NK cytolytic activity by both host and viral ligands.

NK cell autoreactivity and autoimmune diseases

Increasing evidences have pointed out the relevance of natural killer (NK) cells in organ-specific and systemic autoimmune diseases. NK cells bear a plethora of activating and inhibiting receptors that can play a role in regulating reactivity with autologous cells. The activating receptors recognize natural ligands up-regulated on virus-infected or stressed or neoplastic cells. Of note, several autoimmune diseases are thought to be linked to viral infections as one of the first event in inducing autoimmunity. Also, it is conceivable that autoimmunity can be triggered when a dysregulation of innate immunity occurs, activating T and B lymphocytes to react with self-components. This would imply that NK cells can play a regulatory role during adaptive immunity; indeed, innate lymphoid cells (ILCs), comprising the classical CD56⁺ NK cells, have a role in maintaining or alternating tissue homeostasis secreting protective and/or pro-inflammatory cytokines. In addition, NK cells display activating receptors involved in natural cytotoxicity and the activating isoforms of receptors for HLA class I that can interact with healthy host cells and induce damage without any evidence of viral infection or neoplastic-induced alteration. In this context, the interrelationship among ILC, extracellular-matrix components, and mesenchymal stromal cells can be considered a key point for the control of homeostasis. Herein, we summarize evidences for a role of NK cells in autoimmune diseases and will give a point of view of the interplay between NK cells and self-cells in triggering autoimmunity.

Re-evaluation of binding properties of recombinant lymphocyte receptors NKR-P1A and CD69 to chemically synthesized glycans and peptides

The binding of monosaccharides and short peptides to lymphocyte receptors (human CD69 and rat NKR-P1A) was first reported in 1994 and then in a number of subsequent publications. Based on this observation, numerous potentially high-affinity saccharide ligands have been synthesized over the last two decades in order to utilize their potential in antitumor therapy. Due to significant inconsistencies in their reported binding properties, we decided to re-examine the interaction between multiple ligands and CD69 or NKR-P1A. Using NMR titration and isothermal titration calorimetry we were unable to detect the binding of the tested ligands such as N-acetyl-d-hexosamines and oligopeptides to both receptors, which contradicts the previous observations published in more than twenty papers over the last fifteen years.

Revisiting the Prominent Anti-Tumoral Potential of Pre-mNK Cells

Interferon-producing killer dendritic cells (IKDC) were first described for their outstanding anti-tumoral properties. The “IKDC” terminology implied the description of a novel DC subset and initiated a debate on their cellular lineage origin. This debate shifted the focus away from their notable anti-tumoral potential. IKDC were recently redefined as precursors to mature NK (mNK) cells and consequently renamed pre-mNK cells. Importantly, a putative human equivalent of pre-mNK cells was recently associated with improved disease outcome in cancer patients. It is thus timely to revisit the functional attributes as well as the therapeutic potential of pre-mNK cells in line with their newly defined NK-cell precursor function.

Modulation of NK cell function by genetically coupled C-type lectin-like receptor/ligand pairs encoded in the human natural killer gene complex

Functional responses of natural killer (NK) cells including eradication of “harmful” cells and modulation of immune responses are regulated by a broad variety of activating and inhibitory NK receptors. Whereas the leukocyte receptor complex (LRC) encodes for NK receptors of the immunoglobulin superfamily, genes of C-type lectin-like NK receptors are clustered in the mammalian natural killer gene complex (NKC). Besides the thoroughly studied C-type lectin-like receptors NKG2D, CD94/NKG2x, and members of the murine Ly49 subfamily, the NKC also encodes for NK receptors of the less characterized NKRP1 subfamily. The prototypic mouse NKRP1 receptor is Nkrp1c (also known as NK1.1), while human members of the NKRP1 subfamily are NKRP1A, NKp80, and NKp65. The latter are not straight homologs of mouse NKRP1 receptors, but share distinct subfamily-specific traits classifying them as members of the NKRP1 subfamily. Ligands of the human NKPR1 receptors are likewise C-type lectin-like glycoproteins belonging to the CLEC2 subfamily (i.e., LLT1, AICL, and KACL), and are encoded in the NKC in tight genetic linkage to their respective receptors. Similarly, certain members of the mouse NKRP1 subfamily interact with genetically coupled CLEC2 glycoproteins, while the reasons for this intriguing tight genetic linkage remain unknown. Recent studies provided new and unique insights into the expression, interaction, and signaling of NKRP1 receptors and their ligands, thereby substantially advancing our understanding of their function and biology. Here, we review our current knowledge on NKRP1 receptors and their genetically linked CLEC2 ligands with an emphasis on the human receptor/ligand pairs NKRP1A-LLT1, NKp80-AICL, and NKp65-KACL.

Suppression of natural killer cells by sorafenib contributes to prometastatic effects in hepatocellular carcinoma

Sorafenib, a multi-tyrosine kinase inhibitor, is a standard treatment for advanced hepatocellular carcinoma (HCC). The present study was undertaken to determine whether the growth and metastasis of HCC were influenced in mice receiving sorafenib prior to implantation with tumors, and to investigate the in-vivo and in-vitro effect of sorafenib on natural killer (NK) cells. In sorafenib-pretreated BALB/c nu/nu mice and C57BL/6 mice, tumor growth was accelerated, mouse survival was decreased, and lung metastasis was increased. However, the depletion of NK1.1⁺ cells in C57BL/6 mice eliminated sorafenib-mediated pro-metastatic effects. Sorafenib significantly reduced the number of NK cells and inhibited reactivity of NK cells against tumor cells, in both tumor-bearing and tumor-free C57BL/6 mice. Sorafenib down-regulated the stimulatory receptor CD69 in NK cells of tumor-bearing mice, but not in tumor-free mice, and inhibited proliferation of NK92-MI cells, which is associated with the blocking of the PI3K/AKT pathway, and inhibited cytotoxicity of NK cells in response to tumor targets, which was due to impaired ERK phosphorylation. These results suggest immunotherapeutic approaches activating NK cells may enhance the therapeutic efficacy of sorafenib in HCC patients.

β-Adrenergic receptor mediated increases in activation and function of natural killer cells following repeated social disruption

Natural killer (NK) cells are specialized innate lymphocytes important in the early defense against tumor and virus bearing cells. Many factors influence the immune system's effectiveness against pathogens, including stress. Social disruption (SDR) "primes" macrophages/monocytes and dendritic cells thereby enhancing their anti-microbial function. What remains unclear is whether similar responses are evident in NK cells. Current studies investigated the cellular distribution and activation/inhibitory phenotypes of NK cells in the spleen, lung, and blood of C57BL/6 male mice following SDR. Furthermore, cytolytic activity and anti-viral cytokine production of splenic NK cells were determined. Lastly, β-adrenergic receptor (β-AR) signaling was investigated to determine possible mechanisms behind the SDR-induced NK cell alterations. Results indicated NK cells from SDR mice have increased expression of CD16 and CD69 and reduced NKG2a and Ly49a expression on splenic CD3-/DX5+ NK cells indicative of an activated phenotype, both immediately and 14h post-SDR. Administration of propranolol (10mg/kg; non-selective β-adrenergic receptor antagonist) was shown to block these "priming" effects at the 14h time-point. In the lung, SDR had similar effects on activation and inhibitory receptors 14h post-SDR, however no alterations were evident in the blood besides increased NK cells directly after SDR. Additionally, splenic NK cells from SDR mice had increased CD107a surface expression, cytolytic activity, and IFN-γ production was increased upon costimulation with IgG and IL-2 ex vivo. Collectively, these data suggest that social stress "primes" NK cells in the spleen and lung to be more proficient in their cytolytic and anti-viral/tumor effecter functions through β-adrenergic receptor dependent signaling.

Molecular cloning and characterization of porcine indoleamine 2, 3-dioxygenase and its expression in various tissues

In order to confirm the existence of indoleamine 2, 3-dioxygenase (IDO) gene in swine, and to clone the novel gene followed by the molecule structure properties and expression pattern analysis, the porcine mRNA sequences homologous to human IDO were obtained from GenBank database by bioinformatics method. By using RT-PCR, the IDO gene was cloned from porcine endothelial cell line and the accuracy of the nucleic acid sequence was confirmed, and the expression pattern of the gene was detected. The three-dimensional structure model of porcine IDO was built referring to the tertiary structure of human IDO using biological sequence analysis software and database. The results showed that the porcine IDO was identified by sequencing. The nucleotide sequences were confirmed as a novel gene after submitted to Genbank. Porcine IDO was expressed in the lung, thymus, epididymis and anterior chamber with a basic level, however in peripheral blood mononuclear cells (PBMCs) the IDO gene was highly expressed. The three-dimensional structure model of porcine IDO was similar to that of human IDO. It was suggested that identification of the structure information of porcine IDO is essential to further investigate the immunologic function of the gene. Study of IDO on NK cells-mediated xenograft rejection will be a novel therapeutic target for the development of xenotransplantation.

Redefining interferon-producing killer dendritic cells as a novel intermediate in NK-cell differentiation

The cell lineage origin of IFN-producing killer dendritic cells (IKDCs), which exhibit prominent antitumoral activity, has been subject to debate. Although IKDCs were first described as a cell type exhibiting both plasmacytoid DC and natural killer (NK) cell properties, the current view reflects that IKDCs merely represent activated NK cells expressing B220, which were thus renamed B220+ NK cells. Herein, we further investigate the lineage relation of B220+ NK cells with regard to other NK-cell subsets. We surprisingly find that, after adoptive transfer, B220- NK cells did not acquire B220 expression, even in the presence of potent activating stimuli. These findings strongly argue against the concept that B220+ NK cells are activated NK cells. Moreover, we unequivocally show that B220+ NK cells are highly proliferative and differentiate into mature NK cells after in vivo adoptive transfer. Additional phenotypic, functional, and transcriptional characterizations further define B220+ NK cells as immediate precursors to mature NK cells. The characterization of these novel attributes to B220+ NK cells will guide the identification of their ortholog in humans, contributing to the design of potent cancer immunotherapies.

The histone deacetylase inhibitor valproic acid lessens NK cell action against oncolytic virus-infected glioblastoma cells by inhibition of STAT5/T-BET signaling and generation of gamma interferon

Tumor virotherapy has been and continues to be used in clinical trials. One barrier to effective viral oncolysis, consisting of the interferon (IFN) response induced by viral infection, is inhibited by valproic acid (VPA) and other histone deacetylase inhibitors (HDACi). Innate immune cell recruitment and activation have been shown to be deleterious to the efficacy of oncolytic herpes simplex virus (oHSV) infection, and in this report we demonstrate that VPA limits this deleterious response. VPA, administered prior to oHSV inoculation in an orthotopic glioblastoma mouse model, resulted in a decline in NK and macrophage recruitment into tumor-bearing brains at 6 and 24 h post-oHSV infection. Interestingly, there was a robust rebound of recruitment of these cells at 72 h post-oHSV infection. The observed initial decline in immune cell recruitment was accompanied by a reduction in their activation status. VPA was also found to have a profound immunosuppressive effect on human NK cells in vitro. NK cytotoxicity was abrogated following exposure to VPA, consistent with downmodulation of cytotoxic gene expression of granzyme B and perforin at the mRNA and protein levels. In addition, suppression of gamma IFN (IFN-γ) production by VPA was associated with decreased STAT5 phosphorylation and dampened T-BET expression. Despite VPA-mediated immune suppression, mice were not at significantly increased risk for HSV encephalitis. These findings indicate that one of the avenues by which VPA enhances oHSV efficacy is through initial suppression of immune cell recruitment and inhibition of inflammatory cell pathways within NK cells.

Prevention of NKT cell activation accelerates cutaneous wound closure and alters local inflammatory signals

We previously reported that in the absence of NKT cells, wound closure was accelerated in a murine excisional punch wound model. Here, we explored whether purposefully inhibiting NKT cell activation had similar effects on wound closure and the dermal inflammatory response to injury. We found that prevention of NKT cell activation accelerated wound closure in a dose-responsive manner. If anti-CD1d was administered before wounding, NKT cell infiltration into cutaneous wounds was diminished without quantitative changes in cellular infiltrates. Furthermore, prevention of NKT cell activation transiently enhanced the local production of a subset of chemokines, including MIP-2, MCP-1, MIP-1α, and MIP-1β, and altered the relative expression of CD69 and CXCR2 on the surface of both circulating and wound NKT cells. Taken together, these findings suggest that wounding activates NKT cells via CD1d presentation of glycolipid antigen and help further define a role for NKT cells in the regulation of wound inflammation and closure. Many soluble factors have been targeted as potential wound healing therapies, but their clinical success has been limited. Given our findings, the NKT cell may be an attractive target for wound healing therapies.

Attenuation of lung inflammation and fibrosis in CD69-deficient mice after intratracheal bleomycin

Background

Cluster of differentiation 69 (CD69), an early activation marker antigen on T and B cells, is also expressed on activated macrophages and neutrophils, suggesting that CD69 may play a role in inflammatory diseases. To determine the effect of CD69 deficiency on bleomycin(BLM)-induced lung injury, we evaluated the inflammatory response following intratracheal BLM administration and the subsequent fibrotic changes in wild type (WT) and CD69-deficient (CD69^-/-) mice.

Methods

The mice received a single dose of 3 mg/kg body weight of BLM and were sacrificed at 7 or 14 days post-instillation (dpi). Lung inflammation in the acute phase (7 dpi) was investigated by differential cell counts and cytokine array analyses of bronchoalveolar lavage fluid. In addition, lung fibrotic changes were evaluated at 14 dpi by histopathology and collagen assays. We also used reverse transcription polymerase chain reaction to measure the mRNA expression level of transforming growth factor β1 (TGF-β1) in the lungs of BLM-treated mice.

Results

CD69^-/- mice exhibited less lung damage than WT mice, as shown by reductions in the following indices: (1) loss of body weight, (2) wet/dry ratio of lung, (3) cytokine levels in BALF, (4) histological evidence of lung injury, (5) lung collagen deposition, and (6) TGF-β1 mRNA expression in the lung.

Conclusion

The present study clearly demonstrates that CD69 plays an important role in the progression of lung injury induced by BLM.

Recruitment of host's progenitor cells to sites of human amniotic fluid stem cells implantation

The amniotic fluid is a new source of multipotent stem cells with a therapeutic potential for human diseases. Cultured at low cell density, human amniotic fluid stem cells (hAFSCs) were still able to generate colony-forming unit-fibroblast (CFU-F) after 60 doublings, thus confirming their staminal nature. Moreover, after extensive in vitro cell expansion hAFSCs maintained a stable karyotype. The expression of genes, such as SSEA-4, SOX2 and OCT3/4 was confirmed at early and later culture stage. Also, hAFSCs showed bright expression of mesenchymal lineage markers and immunoregulatory properties. hAFSCs, seeded onto hydroxyapatite scaffolds and subcutaneously implanted in nude mice, played a pivotal role in mounting a response resulting in the recruitment of host's progenitor cells forming tissues of mesodermal origin such as fat, muscle, fibrous tissue and immature bone. Implanted hAFSCs migrated from the scaffold to the skin overlying implant site but not to other organs. Given their in vivo: (i) recruitment of host progenitor cells, (ii) homing towards injured sites and (iii) multipotentiality in tissue repair, hAFSCs are a very appealing reserve of stem cells potentially useful for clinical application in regenerative medicine.

Protective immunity against experimental pulmonary cryptococcosis in T cell-depleted mice

Individuals with defects in T cell-mediated immunity (CMI) are highly susceptible to infection with Cryptococcus neoformans. The purpose of these studies was to determine if protection against experimental pulmonary cryptococcosis can be generated in T cell-deficient hosts. BALB/c mice were depleted of CD4⁺and/or CD8⁺ T cells or given an isotype control antibody prior to vaccination with a C. neoformans strain, designated H99γ, previously shown to induce protection against C. neoformans infection in immunocompetent mice. Mice depleted of CD4⁺ or CD8⁺ T cells, but not both subsets, survived an acute pulmonary infection with C. neoformans strain H99γ and a subsequent second challenge with wild-type C. neoformans strain H99. We observed a significant increase in the percentage of CD4⁺ and CD8⁺ T cells expressing the activation marker CD69 in the lungs of mice immunized with C. neoformans strain H99γ prior to a secondary challenge with wild-type cryptococci. CD4⁺ T cells within the lungs of immunized mice also appeared to acquire a predominantly activated effector memory cell phenotype (CD69⁺ CD44⁺ CCR7⁻ CD45RB⁻ CD62L⁻) following a second pulmonary challenge with wild-type C. neoformans, compared to CD4⁺ T cells from naïve mice. Lastly, immunization of immunocompetent mice with C. neoformans strain H99γ prior to depletion of CD4⁺ and/or CD8⁺ T cells resulted in significant protection against a second challenge with wild-type C. neoformans. Our studies demonstrate that protective immunity against pulmonary cryptococcosis can be generated in immunosuppressed hosts, thus supporting the development of cryptococcal vaccines.

Viral load reduction improves activation and function of natural killer cells in patients with chronic hepatitis B

BACKGROUND & AIMS

Natural killer (NK) cells play a major role in anti-viral immunity as first line defense and regulation of virus-specific T cell responses. This study aimed to investigate phenotype and function of NK cells in patients with chronic hepatitis B virus (HBV) infection and to study the effect of anti-viral therapy.

METHODS

Peripheral blood NK cells from 40 chronic HBV patients were compared to NK cells of 25 healthy controls. The effect of entecavir-induced viral load reduction on NK cell phenotype and function was investigated in 15 chronic HBV patients.

RESULTS

NK cell numbers and subset distribution did not differ between HBV patients and normal subjects. In chronic HBV patients, the cytotoxic capacity was retained, but NK cell activation and subsequent IFNγ and TNFα production, especially of the CD56(dim) subset, were strongly hampered. This functional dichotomy was paralleled by an altered activation state, elevated expression of NKG2A, and downregulated expression of CD16 and NKp30, which correlated with serum HBV-DNA load. Anti-viral therapy partially restored NK cell phenotype, as shown by NKG2A downregulation. Moreover, viral replication inhibition improved IFNγ production as a result of an increased ability of CD56(dim) NK cells to become activated de novo. This improved NK cell activation and function which correlated with therapy-induced reduction in serum ALT levels, but not HBV-DNA load.

CONCLUSIONS

The specific defect in CD56(dim) NK cell activation and the reduced capacity to produce anti-viral and Th1-skewing cytokines may play a role in HBV persistence. Restoration of this NK cell cytokine-producing capacity, as achieved by viral load reduction, could therefore contribute to definite clearance of the virus.

Relevance of the mevalonate biosynthetic pathway in the regulation of bone marrow mesenchymal stromal cell-mediated effects on T-cell proliferation and B-cell survival

BACKGROUND

Bone marrow mesenchymal stromal cells can suppress T-lymphocyte proliferation but promote survival of normal and malignant B cells, thus representing a possible target for new therapeutic schemes. Here we defined the effects of cholesterol synthesis inhibitors on the interaction between these mesenchymal stromal cells and T or B lymphocytes.

DESIGN AND METHODS

We exposed mesenchymal stromal cells to inhibitors, such as fluvastatin, of the 3-hydroxy-3-methylglutaryl-coenzyme A reductase, responsible for the synthesis of mevalonate, the precursor of cholesterol. Also, these cells were treated with manumycin A, a farnesyl transferase inhibitor which blocks the mevalonate-dependent isoprenylation of small guanosin triphosphate binding proteins. First, mesenchymal stromal cell morphology, cytoskeleton assembly, cell cycle, survival and cytokine production were evaluated. Then, these cells were co-cultured with either T or B lymphocytes and we analyzed: 1) the inhibition of T-cell proliferation to mitogenic stimuli; 2) B-cell survival.

RESULTS

Fluvastatin altered the assembly of actin microfilaments, inactivated RhoA guanosin triphosphate binding protein, inhibited the S-phase of the cell cycle, induced apoptosis in a small fraction of cells but preserved cytokine production. Preincubation of mesenchymal stromal cells with fluvastatin, or manumycin A, down-regulated the expression of adhesion molecules, reduced cell-to-cell interactions and prevented the inhibition exerted by these stromal cells on CD3/T-cell receptor-induced lymphocyte proliferation. Mevalonic acid could revert morphological, phenotypic and functional effects of fluvastatin. Finally, fluvastatin significantly reduced the mesenchymal stromal cells-mediated rescue of B cells in the presence of dexamethasone, although it did not function in the absence of corticosteroids.

CONCLUSIONS

Fluvastatin-mediated effects on bone marrow mesenchymal stromal cells were conceivably due to the inhibition of isoprenylation of small guanosin triphosphate binding proteins, occurring for the lack of mevalonate. Altogether these findings suggest that drugs acting on the mevalonate biosynthetic pathway can regulate mesenchymal stromal cell-induced T-cell suppression and B-lymphocyte survival.

Synthetic N-acetyl-D-glucosamine based fully branched tetrasaccharide, a mimetic of the endogenous ligand for CD69, activates CD69+ killer lymphocytes upon dimerization via a hydrophilic flexible linker

On the basis of the highly branched ovomucoid-type undecasaccharide that had been shown previously to be an endogenous ligand for CD69 leukocyte receptor, a systematic investigation of smaller oligosaccharide mimetics was performed based on linear and branched N-acetyl-d-hexosamine homooligomers prepared synthetically using hitherto unexplored reaction schemes. The systematic structure-activity studies revealed the tetrasaccharide GlcNAcbeta1-3(GlcNAcbeta1-4)(GlcNAcbeta1-6)GlcNAc (compound 52) and its alpha-benzyl derivative 49 as the best ligand for CD69 with IC(50) as high as 10(-9) M. This compound thus approaches the affinity of the classical high-affinity neoglycoprotein ligand GlcNAc(23)BSA. Compound 68, GlcNAc tetrasaccharide 52 dimerized through a hydrophilic flexible linker, turned out to be effective in activating CD69(+) lymphocytes. It also proved efficient in enhancing natural killing in vitro, decreasing the growth of tumors in vivo, and activating the CD69(+) tumor infiltrating lymphocytes examined ex vivo. This compound is thus a candidate for carbohydrate-based immunomodulators with promising antitumor potential.

Differential activation of NK cells by influenza A pseudotype H5N1 and 1918 and 2009 pandemic H1N1 viruses

Natural killer (NK) cells are the effectors of innate immunity and are recruited into the lung 48 h after influenza virus infection. Functional NK cell activation can be triggered by the interaction between viral hemagglutinin (HA) and natural cytotoxicity receptors NKp46 and NKp44 on the cell surface. Recently, novel subtypes of influenza viruses, such as H5N1 and 2009 pandemic H1N1, transmitted directly to the human population, with unusual mortality and morbidity rates. Here, the human NK cell responses to these viruses were studied. Differential activation of heterogeneous NK cells (upregulation of CD69 and CD107a and gamma interferon [IFN-gamma] production as well as downregulation of NKp46) was observed following interactions with H5N1, 1918 H1N1, and 2009 H1N1 pseudotyped particles (pps), respectively, and the responses of the CD56(dim) subset predominated. Much stronger NK activation was triggered by H5N1 and 1918 H1N1 pps than by 2009 H1N1 pps. The interaction of pps with NK cells and subsequent internalization were mediated by NKp46 partially. The NK cell activation by pps showed a dosage-dependent manner, while an increasing viral HA titer attenuated NK activation phenotypes, cytotoxicity, and IFN-gamma production. The various host innate immune responses to different influenza virus subtypes or HA titers may be associated with disease severity.

Simian recombinant adenovirus delivered by the mucosal route modulates gammadelta T cells from murine genital tract

Although it has been demonstrated that mucosal immunization using vectors such as simian adenovirus (AdC) stimulates robust adaptive immune responses, there remains a paucity of information on the modulation of innate immune responses by such vectors. Using an established murine model of intravaginal immunization (Ivag), we have investigated whether mucosal gammadelta T cells participate in immune responses induced by AdC vectors. gammadelta T cell numbers were found to be increased in the vaginal tract. Moreover, gammadelta T cells isolated from the genital tract showed an activated phenotype and enhanced expression of cytokine gene. Altogether, our results demonstrate that AdC modulates gammadelta T cell responses and suggest that this cell population may influence immune responses following vaginal immunization.

Melanoma-associated fibroblasts modulate NK cell phenotype and antitumor cytotoxicity

Although the role of the tumor microenvironment in the process of cancer progression has been extensively investigated, the contribution of different stromal components to tumor growth and/or evasion from immune surveillance is still only partially defined. In this study we analyzed fibroblasts derived from metastatic melanomas and provide evidence for their strong immunosuppressive activity. In coculture experiments, melanoma-derived fibroblasts sharply interfered with NK cell functions including cytotoxicity and cytokine production. Thus, both the IL-2-induced up-regulation of the surface expression of NKp44, NKp30, and DNAM-1 triggering receptors and the acquisition of cytolytic granules were inhibited in NK cells. This resulted in an impairment of the NK cell-mediated killing of melanoma target cells. Transwell cocultures and the use of specific inhibitors suggested that cell-to-cell contact was required for inducing DNAM-1 modulation. In contrast, modulation of NKp44 and NKp30 was due to PGE(2) released by fibroblasts during coculture. Normal skin fibroblasts could also partially affect NK cell phenotype and function. However, the inhibitory effect of tumor-derived fibroblasts was far stronger and directly correlated with their ability to produce PGE(2) either constitutively or upon induction by NK cells.

CD94 defines phenotypically and functionally distinct mouse NK cell subsets

Understanding of heterogeneous NK subsets is important for the study of NK cell biology and development, and for the application of NK cell-based therapies in the treatment of disease. Here we demonstrate that the surface expression of CD94 can distinctively divide mouse NK cells into two approximately even CD94(low) and CD94(high) subsets in all tested organs and tissues. The CD94(high) NK subset has significantly greater capacity to proliferate, produce IFN-gamma, and lyse target cells than does the CD94(low) subset. The CD94(high) subset has exclusive expression of NKG2A/C/E, higher expression of CD117 and CD69, and lower expression of Ly49D (activating) and Ly49G2 (inhibitory). In vivo, purified mouse CD94(low) NK cells become CD94(high) NK cells, but not vice versa. Collectively, our data suggest that CD94 is an Ag that can be used to identify functionally distinct NK cell subsets in mice and could also be relevant to late-stage mouse NK cell development.

Binding of thymoglobulin to natural killer cells leads to cell activation and interferon-gamma production

Thymoglobulin is an antithymocyte globulin preparation used in hematopoietic stem cell transplantation (HSCT) to prevent rejection and graft-versus-host disease. Because natural killer (NK)-cell alloreactivity improves HSCT outcome, but only in patients receiving thymoglobulin, we investigated the in vitro effects of thymoglobulin on purified NK cells. Thymoglobulin binding to NK cells and NK-cell activation were assessed by flow cytometry. NK surface targets for thymoglobulin were determined by competition inhibition assays using monoclonal antibodies. Chromium 51 (Cr) release assay, Annexin V combined with 7-amino-actinomycin D staining, and carboxyfluorescein diacetate succinimidyl ester staining were used to study cytotoxic activity, apoptosis/cell death, and NK-cell proliferation, respectively. Interferon (IFN)-gamma production was determined by ELISA. Thymoglobulin, thymoglobulin derived-F(ab')2 fragments as well as rabbit IgG bound NK cells, and competed strongly with anti-CD16. Thymoglobulin enhanced the expression of activation (CD69 and NKG2D) and degranulation (CD107a) markers on NK cells. It competed with CD18 binding and decreased NK activity, but not interleukin-15-induced killer activity. Effects on apoptosis/cell death and proliferation were minimal. F(ab')2 fragments and rabbit IgG strongly induced IFN-gamma production by NK cells. Thymoglobulin binds to NK cells by CD16 by its variable and constant regions. The decrease in NK-cell cytotoxic activity is restored by interleukin-15, and contrasts sharply with the induction of activation, degranulation, and IFN-gamma production. These data support the hypothesis that thymoglobulin treatment is required to observe the improvement in HSCT outcome by NK-cell alloreactivity.