Unique subpopulations of CD56+ NK and NK-T peripheral blood lymphocytes identified by chemokine receptor expression repertoire

Comprehensive snapshots of natural killer cells functions, signaling, molecular mechanisms and clinical utilization

Natural killer (NK) cells, initially identified for their rapid virus-infected and leukemia cell killing and tumor destruction, are pivotal in immunity. They exhibit multifaceted roles in cancer, viral infections, autoimmunity, pregnancy, wound healing, and more. Derived from a common lymphoid progenitor, they lack CD3, B-cell, or T-cell receptors but wield high cytotoxicity via perforin and granzymes. NK cells orchestrate immune responses, secreting inflammatory IFNγ or immunosuppressive TGFβ and IL-10. CD56dim and CD56bright NK cells execute cytotoxicity, while CD56bright cells also regulate immunity. However, beyond the CD56 dichotomy, detailed phenotypic diversity reveals many functional subsets that may not be optimal for cancer immunotherapy. In this review, we provide comprehensive and detailed snapshots of NK cells' functions and states of activation and inhibitions in cancer, autoimmunity, angiogenesis, wound healing, pregnancy and fertility, aging, and senescence mediated by complex signaling and ligand-receptor interactions, including the impact of the environment. As the use of engineered NK cells for cancer immunotherapy accelerates, often in the footsteps of T-cell-derived engineering, we examine the interactions of NK cells with other immune effectors and relevant signaling and the limitations in the tumor microenvironment, intending to understand how to enhance their cytolytic activities specifically for cancer immunotherapy.

Cataloging circulating CD3+CD56+ NKT-like cells through a series of stimulating (NKG2D and DNAM-1) and inhibitory (PD-1, TIGIT, and Tim-3) immune checkpoint receptors in women diagnosed with precancerous cervical lesions or invasive cervical carcinoma

Persistent human papillomavirus infection is associated with the development of premalignant lesions that can eventually lead to cervical cancer. In this study, we evaluated the expression of activating (NKG2D, DNAM-1) and inhibitory immune checkpoints receptors (PD-1, TIGIT, and Tim-3) in peripheral blood NKT-like (CD3+CD56+) lymphocytes from patients with cervical carcinoma (CC, n = 19), high-grade lesions (HG, n = 8), low-grade lesions (LG, n = 19) and healthy donors (HD, n = 17) using multiparametric flow cytometry. Dimensional data analysis showed four clusters within the CD3+CD56+ cells with different patterns of receptor expression. We observed upregulation of CD16 in CC and HG patients in one of the clusters. In another, TIGIT was upregulated, while DNAM-1 was downregulated. Throughout manual gating, we observed that NKT-like cells expressing activating receptors also co-express inhibitory receptors (PD-1 and TIGIT), which can affect the activation of these cells. A deeper characterization of the functional state of the cells may help to clarify their role in cervical cancer, as will the characterization of the NKT-like cells as cytotoxic CD8+ T cells or members of type I or type II NKT cells.

Persistence of a Skewed Repertoire of NK Cells in People with HIV-1 on Long-Term Antiretroviral Therapy

HIV-1 infection greatly alters the NK cell phenotypic and functional repertoire. This is highlighted by the expansion of a rare population of FcRγ- NK cells exhibiting characteristics of traditional immunologic memory in people with HIV (PWH). Although current antiretroviral therapy (ART) effectively controls HIV-1 viremia and disease progression, its impact on HIV-1-associated NK cell abnormalities remains unclear. To address this, we performed a longitudinal analysis detailing conventional and memory-like NK cell characteristics in n = 60 PWH during the first 4 y of ART. Throughout this regimen, a skewed repertoire of cytokine unresponsive FcRγ- memory-like NK cells persisted and accompanied an overall increase in NK surface expression of CD57 and KLRG1, suggestive of progression toward immune senescence. These traits were linked to elevated serum inflammatory biomarkers and increasing Ab titers to human CMV, with human CMV viremia detected in approximately one-third of PWH at years 1-4 of ART. Interestingly, 40% of PWH displayed atypical NK cell subsets, representing intermediate stages of NK-poiesis based on single-cell multiomic trajectory analysis. Our findings indicate that NK cell irregularities persist in PWH despite long-term ART, underscoring the need to better understand the causative mechanisms that prevent full restoration of immune health in PWH.

Ozanimod-mediated remission in experimental autoimmune encephalomyelitis is associated with enhanced activity of CNS CD27low/- NK cell subset

Background

Ozanimod (RPC1063) is an immunomodulator that has been recently approved by the FDA (2020) for the treatment of relapsing-remitting multiple sclerosis (RRMS). It is a selective agonist of the sphingosine-1-phophate receptors 1 and 5, expressed on naïve and central memory T and B cells, as well as natural killer (NK) cells, and is involved in lymphocyte trafficking. Oral administration of ozanimod was reported to result in rapid and reversible reduction in circulating lymphocytes in multiple sclerosis (MS) patients, however, only minimal effect on NK cells was observed. In this study, we sought to investigate the effect of ozanimod on NK cells and assess whether they play any role in ozanimod-induced remission in experimental autoimmune encephalomyelitis (EAE), the animal model of MS.

Methods

Active EAE induction was done in C57BL/6 female mice, followed by daily oral treatment with ozanimod (0.6mg/kg) starting at disease onset (score 1). Flow cytometry of blood and CNS was performed 24 hours after the last oral dose of ozanimod treatment in diseased mice. Histological analysis of lumbar spinal cord was performed for evaluating the level of inflammation and demyelination. Depletion of peripheral NK cells was done using anti-NK1.1 mouse antibody (mAb) at day 5 post-EAE induction.

Results

Ozanimod was effective in reducing the clinical severity of EAE and reducing the percentage of autoreactive CD4+ and CD8+ T cells along with significant inhibition of lymphocyte infiltration into the spinal cord, accompanied by reversed demyelination. Furthermore, ozanimod treatment resulted in a significant increase in the frequency of total NK cells in the blood and CNS along with upregulation of the activating receptor NKG2D on CD27low/- NK cell subset in the CNS. The effectiveness of ozanimod treatment in inhibiting the progression of the disease was reduced when NK cells were depleted using anti-NK1.1 mAb.

Conclusion

The current study demonstrated that ozanimod treatment significantly improved clinical symptoms in EAE mice. Ozanimod and anti-NK1.1 mAb appear to function in opposition to one another. Collectively, our data suggest that ozanimod-mediated remission is associated with an increased percentage of total NK cells and CD27low/- NK cells expressing the activating receptor, NKG2D in the CNS.

Distinctive CD56dim NK subset profiles and increased NKG2D expression in blood NK cells of Parkinson's disease patients

Mounting data suggest an important role for the immune system in Parkinson's disease (PD). Previous evidence of increased natural killer (NK) cell populations in PD suggests a potential role of NK cells in the pathogenesis of the disease. Previous studies have analyzed NK cell populations using aggregation by variable expression of CD56 and CD16. It remains unknown what differences may exist between NK cell subpopulations when stratified using more nuanced classification. Here, we profile NK cell subpopulations and elucidate the expressions of activating, NKG2D, inhibitory, NKG2A, and homing, CX3CR1, receptors on NK cell subpopulations in PD and healthy controls (HC). We analyzed cryopreserved PMBC samples using a 10-color flow cytometry panel to evaluate NK cell subpopulations in 31 individuals with sporadic PD and 27 HC participants. Here we identified significant differences in the CD56dim NK subset that changes with disease severity in PD. Furthermore, the expressions of NKG2D in all three NK cell subsets were significantly elevated in PD patients compared to HC. Notably, NKG2A expression in the CD56bright NK subset increased in PD patients with longer disease duration but there were no changes in CX3CR1. In summary, our data suggests that changes in NK cells may be influenced by the clinical severity and duration of PD.

The role of CD56bright NK cells in neurodegenerative disorders

Emerging evidence suggests a potential role for natural killer (NK) cells in neurodegenerative diseases, such as multiple sclerosis, Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. However, the precise function of NK cells in these diseases remains ambiguous. The existence of two NK cell subsets, CD56bright and CD56dim NK cells, complicates the understanding of the contribution of NK cells in neurodegeneration as their functions within the context of neurodegenerative diseases may differ significantly. CD56bright NK cells are potent cytokine secretors and are considered more immunoregulatory and less terminally differentiated than their mostly cytotoxic CD56dim counterparts. Hence, this review focusses on NK cells, specifically on CD56bright NK cells, and their role in neurodegenerative diseases. Moreover, it explores the mechanisms underlying their ability to enter the central nervous system. By consolidating current knowledge, we aim to provide a comprehensive overview on the role of CD56bright NK cells in neurodegenerative diseases. Elucidating their impact on neurodegeneration may have implications for future therapeutic interventions, potentially ameliorating disease pathogenesis.

Endometrial TGFβ signaling fosters early pregnancy development by remodeling the fetomaternal interface

The endometrium is a unique and highly regenerative tissue with crucial roles during the reproductive lifespan of a woman. As the first site of contact between mother and embryo, the endometrium, and its critical processes of decidualization and immune cell recruitment, play a leading role in the establishment of pregnancy, embryonic development, and reproductive capacity. These integral processes are achieved by the concerted actions of steroid hormones and a myriad of growth factor signaling pathways. This review focuses on the roles of the transforming growth factor β (TGFβ) pathway in the endometrium during the earliest stages of pregnancy through the lens of immune cell regulation and function. We discuss how key ligands in the TGFβ family signal through downstream SMAD transcription factors and ultimately remodel the endometrium into a state suitable for embryo implantation and development. We also focus on the key roles of the TGFβ signaling pathway in recruiting uterine natural killer cells and their collective remodeling of the decidua and spiral arteries. By providing key details about immune cell populations and TGFβ signaling within the endometrium, it is our goal to shed light on the intricate remodeling that is required to achieve a successful pregnancy.

Activated NK Cells with Pro-inflammatory Features are Associated with Atherogenesis in Perinatally HIV-Acquired Adolescents

Human immunodeficiency virus (HIV) is associated with persistent immune activation and dysfunction in people with HIV despite treatment with antiretroviral therapy (ART). Modulation of the immune system may be driven by: low-level HIV replication, co-pathogens, gut dysbiosis /translocation, altered lipid profiles, and ART toxicities. In addition, perinatally acquired HIV (PHIV) and lifelong ART may alter the development and function of the immune system. Our preliminary data and published literature suggest reprogramming innate immune cells may accelerate aging and increase the risk for future end-organ complications, including cardiovascular disease (CVD). The exact mechanisms, however, are currently unknown. Natural killer (NK) cells are a highly heterogeneous cell population with divergent functions. They play a critical role in HIV transmission and disease progression in adults. Recent studies suggest the important role of NK cells in CVDs; however, little is known about NK cells and their role in HIV-associated cardiovascular risk in PHIV adolescents. Here, we investigated NK cell subsets and their potential role in atherogenesis in PHIV adolescents compared to HIV-negative adolescents in Uganda. Our data suggest, for the first time, that activated NK subsets in PHIV adolescents may contribute to atherogenesis by promoting plasma oxidized low-density lipoprotein (Ox-LDL) uptake by vascular macrophages.

Mapping human natural killer cell development in pediatric tonsil by imaging mass cytometry and high-resolution microscopy

Natural killer (NK) cells develop from CD34+ progenitors in a stage-specific manner defined by changes in cell surface receptor expression and function. Secondary lymphoid tissues, including tonsil, are sites of human NK cell development. Here we present new insights into human NK cell development in pediatric tonsil using cyclic immunofluorescence and imaging mass cytometry. We show that NK cell subset localization and interactions are dependent on NK cell developmental stage and tissue residency. NK cell progenitors are found in the interfollicular domain in proximity to cytokine-expressing stromal cells that promote proliferation and maturation. Mature NK cells are primarily found in the T-cell rich parafollicular domain engaging in cell-cell interactions that differ depending on their stage and tissue residency. The presence of local inflammation results in changes in NK cell interactions, abundance, and localization. This study provides the first comprehensive atlas of human NK cell development in secondary lymphoid tissue.

Understanding NK cell biology for harnessing NK cell therapies: targeting cancer and beyond

Gene-engineered immune cell therapies have partially transformed cancer treatment, as exemplified by the use of chimeric antigen receptor (CAR)-T cells in certain hematologic malignancies. However, there are several limitations that need to be addressed to target more cancer types. Natural killer (NK) cells are a type of innate immune cells that represent a unique biology in cancer immune surveillance. In particular, NK cells obtained from heathy donors can serve as a source for genetically engineered immune cell therapies. Therefore, NK-based therapies, including NK cells, CAR-NK cells, and antibodies that induce antibody-dependent cellular cytotoxicity of NK cells, have emerged. With recent advances in genetic engineering and cell biology techniques, NK cell-based therapies have become promising approaches for a wide range of cancers, viral infections, and senescence. This review provides a brief overview of NK cell characteristics and summarizes diseases that could benefit from NK-based therapies. In addition, we discuss recent preclinical and clinical investigations on the use of adoptive NK cell transfer and agents that can modulate NK cell activity.

In vitro models to study natural killer cell dynamics in the tumor microenvironment

Immunotherapy is revolutionizing cancer therapy. The rapid development of new immunotherapeutic strategies to treat solid tumors is posing new challenges for preclinical research, demanding novel in vitro methods to test treatments. Such methods should meet specific requirements, such as enabling the evaluation of immune cell responses like cytotoxicity or cytokine release, and infiltration into the tumor microenvironment using cancer models representative of the original disease. They should allow high-throughput and high-content analysis, to evaluate the efficacy of treatments and understand immune-evasion processes to facilitate development of new therapeutic targets. Ideally, they should be suitable for personalized immunotherapy testing, providing information for patient stratification. Consequently, the application of in vitro 3-dimensional (3D) cell culture models, such as tumor spheroids and organoids, is rapidly expanding in the immunotherapeutic field, coupled with the development of novel imaging-based techniques and -omic analysis. In this paper, we review the recent advances in the development of in vitro 3D platforms applied to natural killer (NK) cell-based cancer immunotherapy studies, highlighting the benefits and limitations of the current methods, and discuss new concepts and future directions of the field.

A review of the pleiotropic actions of the IFN-inducible CXC chemokine receptor 3 ligands in the synovial microenvironment

Chemokines are pivotal players in instigation and perpetuation of synovitis through leukocytes egress from the blood circulation into the inflamed articulation. Multitudinous literature addressing the involvement of the dual-function interferon (IFN)-inducible chemokines CXCL9, CXCL10 and CXCL11 in diseases characterized by chronic inflammatory arthritis emphasizes the need for detangling their etiopathological relevance. Through interaction with their mutual receptor CXC chemokine receptor 3 (CXCR3), the chemokines CXCL9, CXCL10 and CXCL11 exert their hallmark function of coordinating directional trafficking of CD4+ TH1 cells, CD8+ T cells, NK cells and NKT cells towards inflammatory niches. Among other (patho)physiological processes including infection, cancer, and angiostasis, IFN-inducible CXCR3 ligands have been implicated in autoinflammatory and autoimmune diseases. This review presents a comprehensive overview of the abundant presence of IFN-induced CXCR3 ligands in bodily fluids of patients with inflammatory arthritis, the outcomes of their selective depletion in rodent models, and the attempts at developing candidate drugs targeting the CXCR3 chemokine system. We further propose that the involvement of the CXCR3 binding chemokines in synovitis and joint remodeling encompasses more than solely the directional ingress of CXCR3-expressing leukocytes. The pleotropic actions of the IFN-inducible CXCR3 ligands in the synovial niche reiteratively illustrate the extensive complexity of the CXCR3 chemokine network, which is based on the intercommunion of IFN-inducible CXCR3 ligands with distinct CXCR3 isoforms, enzymes, cytokines, and infiltrated and resident cells present in the inflamed joints.

Efficient Redirection of NK Cells by Genetic Modification with Chemokine Receptors CCR4 and CCR2B

Natural killer (NK) cells are a subset of lymphocytes that offer great potential for cancer immunotherapy due to their natural anti-tumor activity and the possibility to safely transplant cells from healthy donors to patients in a clinical setting. However, the efficacy of cell-based immunotherapies using both T and NK cells is often limited by a poor infiltration of immune cells into solid tumors. Importantly, regulatory immune cell subsets are frequently recruited to tumor sites. In this study, we overexpressed two chemokine receptors, CCR4 and CCR2B, that are naturally found on T regulatory cells and tumor-resident monocytes, respectively, on NK cells. Using the NK cell line NK-92 as well as primary NK cells from peripheral blood, we show that genetically engineered NK cells can be efficiently redirected using chemokine receptors from different immune cell lineages and migrate towards chemokines such as CCL22 or CCL2, without impairing the natural effector functions. This approach has the potential to enhance the therapeutic effect of immunotherapies in solid tumors by directing genetically engineered donor NK cells to tumor sites. As a future therapeutic option, the natural anti-tumor activity of NK cells at the tumor sites can be increased by co-expression of chemokine receptors with chimeric antigen receptors (CAR) or T cell receptors (TCR) on NK cells can be performed in the future.

Mapping the interplay between NK cells and HIV: therapeutic implications

Although highly effective at durably suppressing plasma HIV-1 viremia, combination antiretroviral therapy (ART) treatment regimens do not eradicate the virus, which persists in long-lived CD4+ T cells. This latent viral reservoir serves as a source of plasma viral rebound following treatment interruption, thus requiring lifelong adherence to ART. Additionally, challenges remain related not only to access to therapy but also to a higher prevalence of comorbidities with an inflammatory etiology in treated HIV-1+ individuals, underscoring the need to explore therapeutic alternatives that achieve sustained virologic remission in the absence of ART. Natural killer (NK) cells are uniquely positioned to positively impact antiviral immunity, in part due to the pleiotropic nature of their effector functions, including the acquisition of memory-like features, and, therefore, hold great promise for transforming HIV-1 therapeutic modalities. In addition to defining the ability of NK cells to contribute to HIV-1 control, this review provides a basic immunologic understanding of the impact of HIV-1 infection and ART on the phenotypic and functional character of NK cells. We further delineate the qualities of "memory" NK cell populations, as well as the impact of HCMV on their induction and subsequent expansion in HIV-1 infection. We conclude by highlighting promising avenues for optimizing NK cell responses to improve HIV-1 control and effect a functional cure, including blockade of inhibitory NK receptors, TLR agonists to promote latency reversal and NK cell activation, CAR NK cells, BiKEs/TriKEs, and the role of HIV-1-specific bNAbs in NK cell-mediated ADCC activity against HIV-1-infected cells.

Peripheral blood persistence and expansion of transferred non-genetically modified Natural Killer cells might not be necessary for clinical activity

Natural killer (NK) cells are innate lymphocytes that react without previous exposition to virus infected or malignant cells and stimulate adaptive immune response to build a long-lasting immunity against it. To that end, tissue resident NK cells are predominantly regulatory as opposed to cytotoxic. In the hematopoietic stem cell transplant (HSCT) setting, which curative potential relies on the graft versus leukemia effect, NK cells are known to play a significant role. This knowledge has paved the way to the active investigation on its anti-tumor effect outside the stem cell transplant scenario. Based on the relevant literature on the adoptive transfer of non-genetically modified NK cells for the treatment of relapsed/refractory acute leukemia and on our own experience, we discuss the role of donor cell peripheral blood persistence and expansion and its lack of correlation with anti-leukemia activity.

Preclinical and clinical studies of CAR-NK-cell therapies for malignancies

The development of chimeric antigen receptor T (CAR-T) cell therapy, a specific type of immunotherapy, in recent decades was a fantastic breakthrough for the treatment of hematological malignancies. However, difficulties in collecting normal T cells from patients and the time cost of manufacturing CAR-T cells have limited the application of CAR-T-cell therapy. In addition, the termination of related clinical trials on universal CAR-T cell therapy has made further research more difficult. Natural killer (NK) cells have drawn great attention in recent years. Chimeric antigen receptor-NK (CAR-NK) cell therapy is a promising strategy in the treatment of malignant tumors because of its lack of potential for causing graft-versus-host disease (GVHD). In this review, we will address the advances in and achievements of CAR-NK cell therapy.

The transcription factor Bach2 negatively regulates murine natural killer cell maturation and function

BTB domain And CNC Homolog 2 (Bach2) is a transcription repressor that actively participates in T and B lymphocyte development, but it is unknown if Bach2 is also involved in the development of innate immune cells, such as natural killer (NK) cells. Here, we followed the expression of Bach2 during murine NK cell development, finding that it peaked in immature CD27+CD11b+ cells and decreased upon further maturation. Bach2 showed an organ and tissue-specific expression pattern in NK cells. Bach2 expression positively correlated with the expression of transcription factor TCF1 and negatively correlated with genes encoding NK effector molecules and those involved in the cell cycle. Lack of Bach2 expression caused changes in chromatin accessibility of corresponding genes. In the end, Bach2 deficiency resulted in increased proportions of terminally differentiated NK cells with increased production of granzymes and cytokines. NK cell-mediated control of tumor metastasis was also augmented in the absence of Bach2. Therefore, Bach2 is a key checkpoint protein regulating NK terminal maturation.

Functional prominence of natural killer cells and natural killer T cells in pregnancy and infertility: A comprehensive review and update

During pregnancy, complicated connections are formed between a mother and a fetus. In a successful pregnancy, the maternal-fetal interface is affected by dynamic changes, and the fetus is protected against the mother's immune system. Natural killer (NK) cells are one of the immune system cells in the female reproductive system that play an essential role in the physiology of pregnancy. NK cells not only exist in peripheral blood (PB) but also can exist in the decidua. Studies have suggested multiple roles for these cells, including decidualization, control of trophoblast growth and invasion, embryo acceptance and maintenance by the mother, and facilitation of placental development during pregnancy. Natural killer T (NKT) cells are another group of NK cells that play a crucial role in the maintenance of pregnancy and regulation of the immune system during pregnancy. Studies show that NK and NKT cells are not only effective in maintaining pregnancy but also can be involved in infertility-related diseases. This review focuses on NK and NKT cells biology and provides a detailed description of the functions of these cells in implantation, placentation, and immune tolerance during pregnancy and their role in pregnancy complications.

Cord Blood-Derived Natural Killer Cell Exploitation in Immunotherapy Protocols: More Than a Promise?

Simple Summary

NK cell anti-tumor activity against hematological malignancies is well-established and many studies support their role in the control of solid tumor growth and metastasis generation. However, tumor microenvironment may affect NK cell function. Ongoing studies are aimed to design novel immunotherapeutic protocols to combine NK cell-based immunotherapy with other therapeutic strategies to improve the anti-tumor NK cell response. In this context, UCB is one of the main sources of both mature NK cells and of CD34⁺ HSPC that can generate NK cells, both in-vivo and in-vitro. UCB-derived NK cells represent a valuable tool to perform in-vitro and preclinical analyses and are already used in several clinical settings, particularly against hematological malignancies. The present review describes the characteristics of different types of UCB-derived NK cells and the in-vitro models to expand them, both for research and clinical purposes in the context of cancer immunotherapy.

Abstract

In the last 20 years, Natural Killer (NK) cell-based immunotherapy has become a promising approach to target various types of cancer. Indeed, NK cells play a pivotal role in the first-line defense against tumors through major histocompatibility complex-independent immunosurveillance. Their role in the control of leukemia relapse has been clearly established and, moreover, the presence of NK cells in the tumor microenvironment (TME) generally correlates with good prognosis. However, it has also been observed that, often, NK cells poorly infiltrate the tumor tissue, and, in TME, their functions may be compromised by immunosuppressive factors that contribute to the failure of anti-cancer immune response. Currently, studies are focused on the design of effective strategies to expand NK cells and enhance their cytotoxic activity, exploiting different cell sources, such as peripheral blood (PB), umbilical cord blood (UCB) and NK cell lines. Among them, UCB represents an important source of mature NK cells and CD34⁺ Hematopoietic Stem and Progenitor Cells (HSPCs), as precursors of NK cells. In this review, we summarize the UCB-derived NK cell activity in the tumor context, review the different in-vitro models to expand NK cells from UCB, and discuss the importance of their exploitation in anti-tumor immunotherapy protocols.

Effective innate immune response in natural HIV-1 controllers. Can mimicking lead to novel preventive and cure strategies against HIV-1?

PURPOSE OF REVIEW

HIV-1 controller individuals represents a model that can be useful for the development of novel vaccines and therapies. Initial studies pointed to the involvement of improved adaptive immunity, however, new emerging evidence suggests the contribution of innate cells to effective antiviral responses in spontaneous controllers. Therefore, understanding the alterations on innate cell subsets might be crucial to develop new effective therapeutic strategies.

RECENT FINDINGS

Among different innate immune cells, dendritic cell (DC) and natural killer (NK) cell are essential for effective antiviral responses. DC from controllers display improved innate detection of HIV-1 transcripts, higher induction of interferons, higher antigen presenting capacities and increased metabolism and higher capacities to induce polyfunctional CD8+ T-cell responses. Such properties have been mimicked by Toll-like receptor ligands and applied to DC-based immunotherapies in humans and in animal models. NK cells from controllers display higher expression of activating receptors promoting increased antibody-dependent cellular cytotoxicity (ADCC) and natural cytotoxicity activities. Neutralizing antibodies in combination with interleukin-15 superagonist or interferon-α can increase ADCC and cytotoxicity in NK cells from HIV-1 progressors.

SUMMARY

Mimicking DC and NK cell innate profiles in controllers has become a promising strategy to step forward a novel efficient immunotherapy against the HIV-1 infection.

Dynamic Changes of Peripheral NK Cells Predict Outcome in Patients with PD-L1 Positive Non-small-cell Lung Cancer Undergoing Immune Checkpoint Inhibitors as Second-line Therapy

We evaluated immune cell frequencies in peripheral blood samples of 41 NSCLC patients before and after second-line therapy with anti-PD-1/PD-L1 agents. Changes in lymphocyte subsets and their correlation with clinical response, progression-free survival (PFS), and overall survival (OS) were analyzed. We observed an increase in median values of all lymphocyte subsets, being significant only for NK cells. A correlation was retrieved between higher post-treatment NK cell level and clinical benefit. On multivariate analysis, PD-L1 tumor proportion score ≥1% and higher post-treatment NK cell counts were predictive of longer PFS and OS. Co-presence of these factors was characterized by longer survival.

Radiotherapy orchestrates natural killer cell dependent antitumor immune responses through CXCL8

Radiotherapy is a mainstay cancer therapy whose antitumor effects partially depend on T cell responses. However, the role of Natural Killer (NK) cells in radiotherapy remains unclear. Here, using a reverse translational approach, we show a central role of NK cells in the radiation-induced immune response involving a CXCL8/IL-8-dependent mechanism. In a randomized controlled pancreatic cancer trial, CXCL8 increased under radiotherapy, and NK cell positively correlated with prolonged overall survival. Accordingly, NK cells preferentially infiltrated irradiated pancreatic tumors and exhibited CD56^dim-like cytotoxic transcriptomic states. In experimental models, NF-κB and mTOR orchestrated radiation-induced CXCL8 secretion from tumor cells with senescence features causing directional migration of CD56^dim NK cells, thus linking senescence-associated CXCL8 release to innate immune surveillance of human tumors. Moreover, combined high-dose radiotherapy and adoptive NK cell transfer improved tumor control over monotherapies in xenografted mice, suggesting NK cells combined with radiotherapy as a rational cancer treatment strategy.

Natural killer cell therapy: A new frontier for obesity-associated cancer

Natural killer (NK) cell infiltration of solid tumours is associated with better outcomes, placing augmentation of NK cell abundance in tumours as an attractive immunotherapeutic approach. The unique ability of NK cells to target cancer cells without antigen specificity increases their versatility and applicability as an immunotherapeutic tool. However, successful utilisation of NK cell-based therapies in solid tumours is still at an early stage. Obesity has become a global health epidemic, and the prevalence of obesity-associated cancers has significantly increased. Obesity-associated malignancies provide a unique challenge for the successful application of cell-based immunotherapies including NK cell-based therapies because significant numbers of NK and T cells are recruited to the visceral adipose tissue at the expense of successful tumour infiltration and eradication. As such, immunotherapy efficacy has been disappointing for obesity-associated malignancies such as oesophageal and gastric adenocarcinoma. Therefore, immunotherapies for obesity-associated cancers warrant our further attention. Indeed, it is becoming ever more obvious that more innovative approaches are needed to re-invigorate anti-tumour immunity and overcome immune exclusion in such tumours. In this review, we briefly summarise the dysfunctionality of NK cells in obesity-associated cancer. We outline the NK cell-based immunotherapeutic approaches which hold promise as effective treatments in this disease space, including CAR-NK cells. Furthermore, we suggest future avenues which possess the potential to transform immunotherapy and specifically NK cell therapy efficacy for obesity-associated cancer.

Tissue Trafficking Kinetics of Rhesus Macaque Natural Killer Cells Measured by Serial Intravascular Staining

The in vivo tissue distribution and trafficking patterns of natural killer (NK) cells remain understudied. Animal models can help bridge the gap, and rhesus macaque (RM) primates faithfully recapitulate key elements of human NK cell biology. Here, we profiled the tissue distribution and localization patterns of three NK cell subsets across various RM tissues. We utilized serial intravascular staining (SIVS) to investigate the tissue trafficking kinetics at steady state and during recovery from CD16 depletion. We found that at steady state, CD16+ NK cells were selectively retained in the vasculature while CD56+ NK cells had a shorter residence time in peripheral blood. We also found that different subsets of NK cells had distinct trafficking kinetics to and from the lymph node as well as other lymphoid and non-lymphoid tissues. Lastly, we found that following administration of CD16-depleting antibody, CD16+ NK cells and their putative precursors retained a high proportion of continuously circulating cells, suggesting that regeneration of the CD16 NK compartment may take place in peripheral blood or the perivascular compartments of tissues.

Myosin 1g and 1f: A Prospective Analysis in NK Cell Functions

NK cells are contained in the ILC1 group; they are recognized for their antiviral and antitumor cytotoxic capacity; NK cells also participate in other immune response processes through cytokines secretion. However, the mechanisms that regulate these functions are poorly understood since NK cells are not as abundant as other lymphocytes, which has made them difficult to study. Using public databases, we identified that NK cells express mRNA encoding class I myosins, among which Myosin 1g and Myosin 1f are prominent. Therefore, this mini-review aims to generate a model of the probable participation of Myosin 1g and 1f in NK cells, based on information reported about the function of these myosins in other leukocytes.

Multifaceted Roles of Chemokines and Chemokine Receptors in Tumor Immunity

Simple Summary

Various immune cells are involved in host immune responses to cancer. T-helper (Th) 1 cells, cytotoxic CD8⁺ T cells, and natural killer cells are the major effector cells in anti-tumor immunity, whereas cells such as regulatory T cells and myeloid-derived suppressor cells are negatively involved in anti-tumor immunity. Th2 cells and Th17 cells have been shown to have both pro-tumor and anti-tumor activities. The migratory properties of various immune cells are essential for their function and critically regulated by the chemokine superfamily. In this review, we summarize the roles of various immune cells in tumor immunity and their migratory regulation by the chemokine superfamily. We also assess the therapeutic possibilities of targeting chemokines and chemokine receptors in cancer immunotherapy.

Abstract

Various immune cells are involved in host tumor immune responses. In particular, there are many T cell subsets with different roles in tumor immunity. T-helper (Th) 1 cells are involved in cellular immunity and thus play the major role in host anti-tumor immunity by inducing and activating cytotoxic T lymphocytes (CTLs). On the other hand, Th2 cells are involved in humoral immunity and suppressive to Th1 responses. Regulatory T (Treg) cells negatively regulate immune responses and contribute to immune evasion of tumor cells. Th17 cells are involved in inflammatory responses and may play a role in tumor progression. However, recent studies have also shown that Th17 cells are capable of directly inducting CTLs and thus may promote anti-tumor immunity. Besides these T cell subsets, there are many other innate immune cells such as dendritic cells (DCs), natural killer (NK) cells, and myeloid-derived suppressor cells (MDSCs) that are involved in host immune responses to cancer. The migratory properties of various immune cells are critical for their functions and largely regulated by the chemokine superfamily. Thus, chemokines and chemokine receptors play vital roles in the orchestration of host immune responses to cancer. In this review, we overview the various immune cells involved in host responses to cancer and their migratory properties regulated by the chemokine superfamily. Understanding the roles of chemokines and chemokine receptors in host immune responses to cancer may provide new therapeutic opportunities for cancer immunotherapy.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Role of Decidual Natural Killer Cells in Human Pregnancy and Related Pregnancy Complications

Pregnancy is a unique type of immunological process. Healthy pregnancy is associated with a series of inflammatory events: implantation (inflammation), gestation (anti-inflammation), and parturition (inflammation). As the most abundant leukocytes during pregnancy, natural killer (NK) cells are recruited and activated by ovarian hormones and have pivotal roles throughout pregnancy. During the first trimester, NK cells represent up to 50–70% of decidua lymphocytes. Differently from peripheral-blood NK cells, decidual natural killer (dNK) cells are poorly cytolytic, and they release cytokines/chemokines that induce trophoblast invasion, tissue remodeling, embryonic development, and placentation. NK cells can also shift to a cytotoxic identity and carry out immune defense if infected in utero by pathogens. At late gestation, premature activation of NK cells can lead to a breakdown of tolerance of the maternal–fetal interface and, subsequently, can result in preterm birth. This review is focused on the role of dNK cells in normal pregnancy and pathological pregnancy, including preeclampsia, recurrent spontaneous abortion, endometriosis, and recurrent implantation failure. dNK cells could be targets for the treatment of pregnancy complications.

Natural killer cell‑based immunotherapy for lung cancer: Challenges and perspectives (Review)

Despite the marked success of molecular targeted therapy in lung cancer in this era of personalized medicine, its efficacy has been limited by the presence of resistance mechanisms. The prognosis of patients with lung cancer remains poor, and there is an unmet need to develop more effective therapies to improve clinical outcomes. The increasing insight into the human immune system has led to breakthroughs in immunotherapy and has prompted research interest in employing immunotherapy to treat lung cancer. Natural killer (NK) cells, which serve as the first line of defense against tumors, can induce the innate and adaptive immune responses. Therefore, the use of NK cells for the development of novel lung-cancer immunotherapy strategies is promising. A growing number of novel approaches that boost NK cell antitumor immunity and expand NK cell populations ex vivo now provide a platform for the development of antitumor immunotherapy. The present review outlined the biology of NK cells, summarized the role of NK cells in lung cancer and the effect of the tumor microenvironment on NK cells, highlighted the potential of NK cell-based immunotherapy as an effective therapeutic strategy for lung cancer and discussed future directions.

The Role of Post-Translational Modifications of Chemokines by CD26 in Cancer

Chemokines are a large family of small chemotactic cytokines that fulfill a central function in cancer. Both tumor-promoting and -impeding roles have been ascribed to chemokines, which they exert in a direct or indirect manner. An important post-translational modification that regulates chemokine activity is the NH₂-terminal truncation by peptidases. CD26 is a dipeptidyl peptidase (DPPIV), which typically clips a NH₂-terminal dipeptide from the chemokine. With a certain degree of selectivity in terms of chemokine substrate, CD26 only recognizes chemokines with a penultimate proline or alanine. Chemokines can be protected against CD26 recognition by specific amino acid residues within the chemokine structure, by oligomerization or by binding to cellular glycosaminoglycans (GAGs). Upon truncation, the binding affinity for receptors and GAGs is altered, which influences chemokine function. The consequences of CD26-mediated clipping vary, as unchanged, enhanced, and reduced activities are reported. In tumors, CD26 most likely has the most profound effect on CXCL12 and the interferon (IFN)-inducible CXCR3 ligands, which are converted into receptor antagonists upon truncation. Depending on the tumor type, expression of CD26 is upregulated or downregulated and often results in the preferential generation of the chemokine isoform most favorable for tumor progression. Considering the tight relationship between chemokine sequence and chemokine binding specificity, molecules with the appropriate characteristics can be chemically engineered to provide innovative therapeutic strategies in a cancer setting.

Cytomegalovirus Infection Impairs the Mobilization of Tissue-Resident Innate Lymphoid Cells into the Peripheral Blood Compartment in Response to Acute Exercise

Circulating immune cell numbers and phenotypes are impacted by high-intensity acute bouts of exercise and infection history with the latent herpesviruses cytomegalovirus (CMV). In particular, CMV infection history impairs the exercise-induced mobilization of cytotoxic innate lymphoid cells 1 (ILC1) cells, also known as NK cells, in the blood. However, it remains unknown whether exercise and CMV infection modulate the mobilization of traditionally tissue-resident non-cytotoxic ILCs into the peripheral blood compartment. To address this question, 22 healthy individuals with or without CMV (20–35 years—45% CMV^pos) completed 30 min of cycling at 70% VO₂ max, and detailed phenotypic analysis of circulating ILCs was performed at rest and immediately post-exercise. We show for the first time that a bout of high-intensity exercise is associated with an influx of ILCs that are traditionally regarded as tissue-resident. In addition, this is the first study to highlight that latent CMV infection blunts the exercise-response of total ILCs and progenitor ILCs (ILCPs). These promising data suggest that acute exercise facilitates the circulation of certain ILC subsets, further advocating for the improvements in health seen with exercise by enhancing cellular mobilization and immunosurveillance, while also highlighting the indirect deleterious effects of CMV infection in healthy adults.

A phase I/II clinical trial on the efficacy and safety of NKT cells combined with gefitinib for advanced EGFR-mutated non-small-cell lung cancer

Background

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib, have achieved good efficacy in EGFR mutation-positive non-small-cell lung cancer (NSCLC) patients, but eventual drug resistance is inevitable. Thus, new TKI-based combination therapies should be urgently explored to extend the overall survival time of these patients. CD8 + CD56+ natural killer T (NKT) cells are a natural and unique subset of lymphocytes in humans that present characteristics of T and NK cells and exert cytotoxicity on tumour cells in a granzyme B-dependent manner. The aim of this trial was to explore the efficacy and safety of CD8 + CD56+ NKT cell immunotherapy combined with gefitinib in patients with advanced EGFR-mutated NSCLC.

Methods

The study was designed as a prospective, randomized, controlled, open-label, phase I/II trial that includes 30 patients with EGFR mutation-positive stage III/IV NSCLC. All patients will be randomized in blocks at a 1:1 ratio and treated with gefitinib 250 mg/day monotherapy or combination therapy with allogeneic CD8 + CD56+ NKT cell infusions twice per month for 12 cycles or until disease progression occurs. The effectiveness of this treatment will be evaluated based on by progression-free survival (PFS), the time to progression (TTP), overall response rate (ORR), disease control rate (DCR) and overall survival (OS). The safety of the trail is being assessed based on adverse events (AEs). Recruitment and data collection, which started in December 2017, are ongoing.

Discussion

Although immunotherapy, including programmed death-1/programmed death-1 ligand (PD-1/PD-L1) immunotherapy, has been used for NSCLC treatment with or without EGFR-TKIs, its clear efficacy still has not been shown. Assessing the safety and therapeutic potential of allogeneic CD8 + CD56+ NKT killer cells in combination with EGFR-TKIs in NSCLC will be of great interest.

Trial registration

This trial (Phase I/II Trails of NKT Cell in Combination With Gefitinib For Non Small Cell Lung Cancer) was registered on 21 November 2017 with www.chictr.org.cn, ChiCTR-IIR-17013471.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08590-1.

Fractalkine Elicits Chemotactic, Phenotypic, and Functional Effects on CX3CR1+CD27- NK Cells in Obesity-Associated Cancer

Esophagogastric adenocarcinomas (EAC) are obesity-associated malignancies underpinned by severe immune dysregulation and inflammation. Our previous work indicates that NK cells migrate to EAC omentum, where they undergo phenotypic and functional alterations and apoptosis. In this study, we investigate whether such erroneous chemotaxis to omentum is paralleled by compromised NK cell infiltration of EAC patient tumor and examine the role of the inflammatory chemokine fractalkine in shaping the NK cell-mediated response. Our data show diminished NK cell frequencies in EAC tumor compared with those in the circulation and reveal that intratumoral NK cell frequencies decline as visceral obesity increases in EAC patients. Our in vitro findings demonstrate that antagonism of fractalkine receptor CX3CR1 significantly reduces NK cell migration to EAC patient-derived, omental adipose tissue-conditioned media, but not toward tumor-conditioned media. These data suggest fractalkine is a key driver of NK cell chemotaxis to omentum but has a lesser role in NK cell homing to tumor in EAC. We propose that this may offer a novel therapeutic strategy to limit NK cell depletion in the omentum of obese EAC patients, and our data suggest the optimal timing for CX3CR1 antagonism is after neoadjuvant chemoradiotherapy. Our functional studies demonstrate that fractalkine induces the conversion from CX3CR1⁺CD27^- to CX3CR1^-CD27⁺ NK cells and increases their IFN-γ and TNF-α production, indicative of its role in shaping the dominant NK cell phenotype in EAC omentum. This study uncovers crucial and potentially druggable pathways underpinning NK cell dysfunction in obesity-associated cancer and provides compelling insights into fractalkine's diverse biological functions.

The Impact of NK Cell-Based Therapeutics for the Treatment of Lung Cancer for Biologics: Targets and Therapy

Lung cancer has a dismal prognosis and novel targeted therapies leave still room for major improvements and better outcomes. Immunotherapy targeting immune checkpoint (IC) proteins, either as single agents or in combination with chemotherapy, is active but responders constitute only approximately 10-15% of non-small cell lung cancer (NSCLC) patients. Other effector immune cells such as CAR-T cells or NK cells may help to overcome the limitations of the IC inhibitor therapies for lung cancer. NK cells can kill tumor cells without previous priming and are present in the circulatory system and lymphoid organs. Tissue-residing NK cells differ from peripheral effector cells and, in case of the lung, comprise CD56bright CD16-negative populations showing high cytokine release but low cytotoxicity in contrast to the circulating CD56dim CD16-positive NK cells exhibiting high cytotoxic efficacy. This local attenuation of NK cell killing potency seems due to a specific stage of NK differentiation, immunosuppressive factors as well as presence of myeloid-derived suppressor cells (MDSCs) and regulatory T cells (TREGs). Improved NK cell-based immunotherapies involve IL-2-stimulated effector cells, NK cells expanded with the help of cytokines, permanent NK cell lines, induced pluripotent stem cell-derived NK cells and NK cells armed with chimeric antigen receptors. Compared to CAR T cell therapy, NK cells administration is devoid of graft-versus-host disease (GvHD) and cytokine-release syndrome. Although NK cells are clearly active against lung cancer cells, the low-cytotoxicity differentiation state in lung tumors, the presence of immunosuppressive leucocyte populations, limited infiltration and adverse conditions of the microenvironment need to be overcome. This goal may be achieved in the future using large numbers of activated and armed NK cells as provided by novel methods in NK cell isolation, expansion and stimulation of cytotoxic activity, including combinations with monoclonal antibodies in antibody-dependent cytotoxicity (ADCC). This review discusses the basic characteristics of NK cells and the potential of NK cell preparations in cancer therapy.

Stem cells-derived natural killer cells for cancer immunotherapy: current protocols, feasibility, and benefits of ex vivo generated natural killer cells in treatment of advanced solid tumors

Nowadays, natural killer (NK) cell-based immunotherapy provides a practical therapeutic strategy for patients with advanced solid tumors (STs). This approach is adaptively conducted by the autologous and identical NK cells after in vitro expansion and overnight activation. However, the NK cell-based cancer immunotherapy has been faced with some fundamental and technical limitations. Moreover, the desirable outcomes of the NK cell therapy may not be achieved due to the complex tumor microenvironment by inhibition of intra-tumoral polarization and cytotoxicity of implanted NK cells. Currently, stem cells (SCs) technology provides a powerful opportunity to generate more effective and universal sources of the NK cells. Till now, several strategies have been developed to differentiate types of the pluripotent and adult SCs into the mature NK cells, with both feeder layer-dependent and/or feeder laye-free strategies. Higher cytokine production and intra-tumoral polarization capabilities as well as stronger anti-tumor properties are the main features of these SCs-derived NK cells. The present review article focuses on the principal barriers through the conventional NK cell immunotherapies for patients with advanced STs. It also provides a comprehensive resource of protocols regarding the generation of SCs-derived NK cells in an ex vivo condition.

Fingolimod Therapy in Multiple Sclerosis Leads to the Enrichment of a Subpopulation of Aged NK Cells

Fingolimod is an approved oral treatment for relapsing-remitting multiple sclerosis (RRMS) that modulates agonistically the sphingosin-1-phosphate receptor (S1PR), inhibiting thereby the egress of lymphocytes from the lymph nodes. In this interventional prospective clinical phase IV trial, we longitudinally investigated the impact of fingolimod on frequencies of NK cell subpopulations by flow cytometry in 17 RRMS patients at baseline and 1, 3, 6, and 12 months after treatment initiation. Clinical outcome was assessed by the Expanded Disability Status Scale (EDSS) and annualized relapse rates (ARR). Over the study period, median EDSS remained stable from month 3 to month 12, and ARR decreased compared to ARR in the 24 months prior treatment. Treatment was paralleled by an increased frequency of circulating NK cells, due primarily to an increase in CD56dimCD94low mature NK cells, while the CD56bright fraction and CD127+ innate lymphoid cells (ILCs) decreased over time. An unsupervised clustering algorithm further revealed that a particular fraction of NK cells defined by the expression of CD56dimCD16++KIR+/-NKG2A-CD94-CCR7+/-CX3CR1+/-NKG2C-NKG2D+NKp46-DNAM1++CD127+ increased during treatment. This specific phenotype might reflect a status of aged, fully differentiated, and less functional NK cells. Our study confirms that fingolimod treatment affects both NK cells and ILC. In addition, our study suggests that treatment leads to the enrichment of a specific NK cell subset characterized by an aged phenotype. This might limit the anti-microbial and anti-tumour NK cell activity in fingolimod-treated patients.

Uterine natural killer cells: from foe to friend in reproduction

BACKGROUND

Recurrent miscarriage and pre-eclampsia are common reproductive disorders, but their causes are often unknown. Recent evidence has provided new insight into immune system influences in reproductive disorders. A subset of lymphocytes of the innate immune system known as uterine natural killer (uNK) cells are now recognized as fundamental to achieving embryo implantation and successful pregnancy, but were initially attributed a bad reputation. Indeed, immune therapies have been developed to treat the 'exaggerated' immune response from uNK cells. These treatments have been based on studies of peripheral blood natural killer (pbNK) cells. However, uNK cells and pbNK cells have different phenotypic and functional characteristics. The functions of uNK cells are closely related to their interactions with the extravillous trophoblast cells (EVTs) and spiral arteries, which underlie an essential role in regulating vascular function, controlling trophoblast invasion and promoting placental development. EVTs express MHC molecules of class I HLA-C/E/G/F, while uNK cells express, among other receptors, killer cell immunoglobulin-like receptors (KIRs) that bind to HLA-C or CD94/NKG2A inhibitory receptors, and then bind HLA-E. Associations of certain KIR/HLA-C combinations with recurrent miscarriage, pre-eclampsia, and foetal growth restriction and the interactions between uNK cells, trophoblasts and vascular cells have led to the hypothesis that uNK cells may play a role in embryo implantation.

OBJECTIVE AND RATIONALE

Our objective was to review the evolution of our understanding of uNK cells, their functions, and their increasingly relevant role in reproduction.

SEARCH METHODS

Relevant literature through June 2020 was retrieved using Google Scholar and PubMed. Search terms comprised uNK cells, human pregnancy, reproductive failure, maternal KIR and HLA-C, HLA-E/G/F in EVT cells, angiogenic cytokines, CD56+ NK cells, spiral artery, oestrogen and progesterone receptors, KIR haplotype and paternal HLA-C2.

OUTCOMES

This review provides key insights into the evolving conceptualization of uNK cells, from their not-so-promising beginnings to now, when they are considered allies in reproduction. We synthesized current knowledge about uNK cells, their involvement in reproduction and their main functions in placental vascular remodeling and trophoblast invasion. One of the issues that this review presents is the enormous complexity involved in studying the immune system in reproduction. The complexity in the immunology of the maternal-foetal interface lies in the great variety of participating molecules, the processes and interactions that occur at different levels (molecular, cellular, tissue, etc.) and the great diversity of genetic combinations that are translated into different types of responses.

WIDER IMPLICATIONS

Insights into uNK cells could offer an important breakthrough for ART outcomes, since each patient could be assessed based on the combination of HLA and its receptors in their uNK cells, evaluating the critical interactions at the materno-foetal interface. However, owing to the technical challenges in studying uNK cells in vivo, there is still much knowledge to gain, particularly regarding their exact origin and functions. New studies using novel molecular and genetic approaches can facilitate the identification of mechanisms by which uNK cells interact with other cells at the materno-foetal interface, perhaps translating this knowledge into clinical applicability.

Dynamic regulation of innate lymphoid cells in the mucosal immune system

The mucosal immune system is considered a local immune system, a term that implies regional restriction. Mucosal tissues are continually exposed to a wide range of antigens. The regulation of mucosal immune cells is tightly associated with the progression of mucosal diseases. Innate lymphoid cells (ILCs) are abundant in mucosal barriers and serve as first-line defenses against pathogens. The subtype changes and translocation of ILCs are accompanied by the pathologic processes of mucosal diseases. Here, we review the plasticity and circulation of ILCs in the mucosal immune system under physiological and pathological conditions. We also discuss the signaling pathways involved in dynamic ILC changes and the related targets in mucosal diseases.

Does exercise attenuate age- and disease-associated dysfunction in unconventional T cells? Shining a light on overlooked cells in exercise immunology

Unconventional T Cells (UTCs) are a unique population of immune cells that links innate and adaptive immunity. Following activation, UTCs contribute to a host of immunological activities, rapidly responding to microbial and viral infections and playing key roles in tumor suppression. Aging and chronic disease both have been shown to adversely affect UTC numbers and function, with increased inflammation, change in body composition, and physical inactivity potentially contributing to the decline. One possibility to augment circulating UTCs is through increased physical activity. Acute exercise is a potent stimulus leading to the mobilization of immune cells while the benefits of exercise training may include anti-inflammatory effects, reductions in fat mass, and improved fitness. We provide an overview of age-related changes in UTCs, along with chronic diseases that are associated with altered UTC number and function. We summarize how UTCs respond to acute exercise and exercise training and discuss potential mechanisms that may lead to improved frequency and function.

Rheumatoid Arthritis Susceptibility Is Associated with the KIR2DS4-Full of Killer-Cell Immunoglobulin-Like Receptor Genes in the Lur Population of Iran

Background

The pathophysiology underlying the progression and development of autoimmune conditions, such as Rheumatoid Arthritis (RA), is a result of dysregulations of the immune system. Research has explored the genetic alterations present in RA; however, limited studies have examined the role of Killer cell Immunoglobulin-like Receptors (KIR) and Human Leukocyte Antigen (HLA) molecules in RA. Therefore, the aim of this study was to examine KIR genes, their HLA ligands, and KIR-HLA compounds in patients with RA.

Methods

In this case-control study, a total of 50 patients with RA and 100 healthy individuals were enrolled. DNA samples were evaluated using PCR with sequence specific Primers (PCR-SSP). Odds ratio (OR) with a 95% confidence interval (CI) were reported.

Results

Among the KIR genes examined, KIR2DLA (p= 0.0255, OR= 0.389, 95% CI= 0.210-0.722) and KIR2DS4-full (p< 0.0001, OR= 6.163, 95% CI= 3.174-11.968) were observed to have a statistically significant correlation with disease susceptibility to RA. As an inhibitory gene, KIR2DLA was observed to have a protective effect against RA while KIR2DS4-full as an activating gene, was found to increase risk for RA. No significant associations were found between any of the other KIR genotypes, HLA ligands, or KIR-HLA compounds examined in this study to RA susceptibility.

Conclusion

In this study of RA in the Lur population of Iran, KIR2DS4-full was observed to increase susceptibility to RA, while KIR2DL5A was found to act as a protecting factor based on both the cross Table and regression analyses. Further research should focus on repeating this study in additional populations.

Targeting NK Cells to Enhance Melanoma Response to Immunotherapies

Natural killer (NK) cells are a key component of an innate immune system. They are important not only in initiating, but also in augmenting adaptive immune responses. NK cell activation is mediated by a carefully orchestrated balance between the signals from inhibitory and activating NK cell receptors. NK cells are potent producers of proinflammatory cytokines and are also able to elicit strong antitumor responses through secretion of perforin and granzyme B. Tumors can develop many mechanisms to evade NK cell antitumor responses, such as upregulating ligands for inhibitory receptors, secreting anti-inflammatory cytokines and recruiting immunosuppressive cells. Enhancing NK cell responses will likely augment the effectiveness of immunotherapies, and strategies to accomplish this are currently being evaluated in clinical trials. A comprehensive understanding of NK cell biology will likely provide additional opportunities to further leverage the antitumor effects of NK cells. In this review, we therefore sought to highlight NK cell biology, tumor evasion of NK cells and clinical trials that target NK cells.

Adenovirus-engineered human dendritic cells induce natural killer cell chemotaxis via CXCL8/IL-8 and CXCL10/IP-10

Recombinant adenovirus-engineered dendritic cells (Ad.DC) are potent vaccines for induction of anti-viral and anti-cancer T cell immunity. The effectiveness of Ad.DC vaccines may depend on the newly described ability of Ad.DC to crosstalk with natural killer (NK) cells via cell-to-cell contact, and to mediate activation, polarization and bridging of innate and adaptive immunity. For this interaction to occur in vivo, Ad.DC must be able to attract NK cells from surrounding tissues or peripheral blood. We developed a novel live mouse imaging system-based NK-cell migration test, and demonstrated for the first time that human Ad.DC induced directional migration of human NK cells across subcutaneous tissues, indicating that Ad.DC-NK cell contact and interaction could occur in vivo. We examined the mechanism of Ad.DC-induced migration of NK cells in vitro and in vivo. Ad.DC produced multiple chemokines previously reported to recruit NK cells, including immunoregulatory CXCL10/IP-10 and proinflammatory CXCL8/IL-8. In vitro chemotaxis experiments utilizing neutralizing antibodies and recombinant human chemokines showed that CXCL10/IP-10 and CXCL8/IL-8 were critical for Ad.DC-mediated recruitment of CD56^hiCD16^- and CD56^loCD16⁺ NK cells, respectively. The importance of CXCL8/IL-8 was further demonstrated in vivo. Pretreatment of mice with the neutralizing anti-CXCL8/IL-8 antibody led to significant inhibition of Ad.DC-induced migration of NK cells in vivo. These data show that Ad.DC can recruit spatially distant NK cells toward a vaccine site via specific chemokines. Therefore, an Ad.DC vaccine can likely induce interaction with endogenous NK cells via transmembrane mediators, and consequently mediate Th1 polarization and amplification of immune functions in vivo.

Overexpressed CXCR4 and CCR7 on the surface of NK92 cell have improved migration and anti-tumor activity in human colon tumor model

Successive infusion of natural killer cells is increasingly being explored as a treatment for cancer patients. The inadequate homing of natural killer cells into the tumor site resulted in the poor efficacy of natural killer cells on solid tumors. For the adoptive transfer of tumor-directed natural killer cell has been proved effective, it is hypothesized that there must be more association between the tumor-produced chemokines and the natural killer cells-expressed chemokine receptors. Increased CXCL12 and CCL21 could ameliorated colorectal cancer via generating an anti-tumor environment by preferentially attracting natural killer cells which expressed the chemokine receptor CXCR4 and CCR7. This study demonstrated that overexpressed CXCR4 and CCR7 on the surface of NK92 cell enhanced their migration to human colon cells. Moreover, the administration of such natural killer cells resulted in tumor shrinkage and a significantly increased survival of experimental mice when compared to ones undergoing the treatment of xenografts with natural killer cells expressing only the mock control. These suggested that chemokine receptor engineered natural killer cells could be a promising tool to improve adoptive tumor immunotherapy.

Persistence of mature dendritic cells, TH2A, and Tc2 cells characterize clinically resolved atopic dermatitis under IL-4Rα blockade

Therapeutic options for autoimmune diseases typically consist of broad and targeted immunosuppressive agents. However, sustained clinical benefit is rarely achieved, as the disease phenotype usually returns after cessation of treatment. To better understand tissue-resident immune memory in human disease, we investigated patients with atopic dermatitis (AD) who underwent short-term or long-term treatment with the IL-4Rα blocker dupilumab. Using multi-omics profiling with single-cell RNA sequencing and multiplex proteomics, we found significant decreases in overall skin immune cell counts and normalization of transcriptomic dysregulation in keratinocytes consistent with clearance of disease. However, we identified specific immune cell populations that persisted for up to a year after clinical remission while being absent from healthy controls. These populations included LAMP3 + CCL22+ mature dendritic cells, CRTH2 + CD161 + T helper ("TH2A") cells, and CRTAM + cytotoxic T cells, which expressed high levels of CCL17 (dendritic cells) and IL13 (T cells). TH2A cells showed a characteristic cytokine receptor constellation with IL17RB, IL1RL1 (ST2), and CRLF2 expression, suggesting that these cells are key responders to the AD-typical epidermal alarmins IL-25, IL-33, and TSLP, respectively. We thus identified disease-linked immune cell populations in resolved AD indicative of a persisting disease memory, facilitating a rapid response system of epidermal-dermal cross-talk between keratinocytes, dendritic cells, and T cells. This observation may help to explain the disease recurrence upon termination of immunosuppressive treatments in AD, and it identifies potential disease memory-linked cell types that may be targeted to achieve a more sustained therapeutic response.

Influenza A Virus Hemagglutinin and Other Pathogen Glycoprotein Interactions with NK Cell Natural Cytotoxicity Receptors NKp46, NKp44, and NKp30

Natural killer (NK) cells are part of the innate immunity repertoire, and function in the recognition and destruction of tumorigenic and pathogen-infected cells. Engagement of NK cell activating receptors can lead to functional activation of NK cells, resulting in lysis of target cells. NK cell activating receptors specific for non-major histocompatibility complex ligands are NKp46, NKp44, NKp30, NKG2D, and CD16 (also known as FcγRIII). The natural cytotoxicity receptors (NCRs), NKp46, NKp44, and NKp30, have been implicated in functional activation of NK cells following influenza virus infection via binding with influenza virus hemagglutinin (HA). In this review we describe NK cell and influenza A virus biology, and the interactions of influenza A virus HA and other pathogen lectins with NK cell natural cytotoxicity receptors (NCRs). We review concepts which intersect viral immunology, traditional virology and glycobiology to provide insights into the interactions between influenza virus HA and the NCRs. Furthermore, we provide expert opinion on future directions that would provide insights into currently unanswered questions.

Elevated NK-cell transcriptional signature and dysbalance of resting and activated NK cells in atopic dermatitis

BACKGROUND

Altered quantities, activity, and composition of natural killer (NK) cells in blood as well as expression changes of genes involved in NK-cell function in skin lesions of patients with atopic dermatitis (AD) were recently reported.

OBJECTIVES

We sought to comprehensively analyze cutaneous NK-cell transcriptomic signatures in AD, and to examine changes under treatment.

METHODS

We analyzed NK-cell signatures in skin transcriptome data from 57 patients with moderate to severe AD and 31 healthy controls. In addition, changes after 12 weeks of systemic treatment (dupilumab n = 21, cyclosporine n = 8) were analyzed. Deconvolution of leucocyte fractions was conducted. Immunofluorescence staining of NK cells was performed on paraffin-embedded skin sections.

RESULTS

Immunofluorescence staining revealed a relatively high abundance of both NK cells and CD3⁺CD56⁺ cells in lesional as compared with nonlesional and healthy skin. Lesional and to a lesser extent nonlesional skin showed a strong upregulation of NK-cell markers together with a dysbalanced expression of inhibitory and activating receptors, which was not reverted under treatment. Digital cytometry showed a decrease in activated and an increase in resting NK cells in both lesional and nonlesional skin, which was reverted by both treatment with dupilumab and cyclosporine. The NK-cell transcriptomic signature remained upregulated after treatment, but there was a shift on the qualitative level, indicating a compositional change in NK-cell subsets toward CD56^bright NK cells.

CONCLUSIONS

Lesional AD skin shows a NK-cell dysregulation, which despite clinical improvement under systemic therapy was only partially reverted, and which may represent a yet underappreciated disease mechanism.

CCL25 Signaling in the Tumor Microenvironment

Multiple checkpoint mechanisms are overridden by cancer cells in order to develop into a tumor. Neoplastic cells, while constantly changing during the course of cancer progression, also craft their surroundings to meet their growing needs. This crafting involves changing cell surface receptors, affecting response to extracellular signals and secretion of signals that affect the nearby cells and extracellular matrix architecture. This chapter briefly comprehends the non-cancer cells facilitating the cancer growth and elaborates on the notable role of the CCR9-CCL25 chemokine axis in shaping the tumor microenvironment (TME), directly and via immune cells. Association of increased CCR9 and CCL25 levels in various tumors has demonstrated the significance of this axis as a tool commonly used by cancer to flourish. It is involved in attracting immune cells in the tumor and determining their fate via various direct and indirect mechanisms and, leaning the TME toward immunosuppressive state. Besides, elevated CCR9-CCL25 signaling allows survival and rapid proliferation of cancer cells in an otherwise repressive environment. It modulates the intra- and extracellular protein matrix to instigate tumor dissemination and creates a supportive metastatic niche at the secondary sites. Lastly, this chapter abridges the latest research efforts and challenges in using the CCR9-CCL25 axis as a cancer-specific target.

Comprehensive Analyses of Type 1 Diabetes Ketosis- or Ketoacidosis-Related Genes in Activated CD56+CD16+ NK Cells

OBJECTIVES

Alterations in natural killer (NK) cells activity cause damage to pancreatic islets in type 1 diabetes mellitus (T1DM). The aim of this study is to identify T1DM ketosis- or ketoacidosis-related genes in activated CD56⁺CD16⁺ NK cells.

METHODS

Microarray datasets were downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were analyzed using the GEO2R tool. Enrichment analyses were performed using Metascape online database and GSEA software. Cell-specific gene co-expression network was built using NetworkAnalyst tools. Cytoscape software was used to identify hub genes and construct co-expressed networks. Target miRNAs were predicted based on the DIANA-micro T, miRDB, and miRWalk online databases.

RESULTS

A total of 70 DEGs were identified between T1DM patients recovered from ketosis or ketoacidosis and healthy control blood samples in GSE44314. Among the DEGs, 10 hub genes were screened out. The mature NK cell-specific gene co-expression network for DEGs in T1DM was built using NetworkAnalyst tools. DEGs between activated CD56⁺CD16⁺ NK cells and CD56^brightCD16^- NK cells were identified from GSE1511. After intersection, 13 overlapping genes between GSE44314 and GSE1511 microarray datasets were screened out, in which 7 hub genes were identified. Additionally, 59 target miRNAs were predicted according to the 7 hub genes. After validating with the exosome miRNA expression profile dataset of GSE97123, seven differentially expressed miRNAs (DEmiRNAs) in plasma-derived exosome were selected. Finally, a mRNA-miRNA network was constructed, which was involved in the T1DM ketosis or ketoacidosis process.

CONCLUSION

This work identified seven hub genes in activated CD56⁺CD16⁺ NK cells and seven miRNAs in plasma-derived exosome as potential predictors of T1DM ketoacidosis, which provided a novel insight for the pathogenesis at the transcriptome level.

Tumor-Infiltrating Natural Killer Cells

Because of their potent antitumor activity and their proinflammatory role, natural killer (NK) cells are at the forefront of efforts to develop immuno-oncologic treatments. NK cells participate in immune responses to tumors by killing target cells and producing cytokines. However, in the immunosuppressive tumor microenvironment, NK cells become dysfunctional through exposure to inhibitory molecules produced by cancer cells, leading to tumor escape. We provide an overview of what is known about NK tumor infiltration and surveillance and about the mechanisms by which NK cells become dysfunctional. SIGNIFICANCE: The functions of tumor-infiltrating NK cells may be impaired. This review aims to describe the various mechanisms by which tumors alter NK-cell functions.