Natural Killer Cells In Control Research Articles

Dysfunctional natural killer cells can be reprogrammed to regain anti-tumor activity

Natural killer (NK) cells are critical to the innate immune system, as they recognize antigens without prior sensitization, and contribute to the control and clearance of viral infections and cancer. However, a significant proportion of NK cells in mice and humans do not express classical inhibitory receptors during their education process and are rendered naturally “anergic”, i.e., exhibiting reduced effector functions. The molecular events leading to NK cell anergy as well as their relation to those underlying NK cell exhaustion that arises from overstimulation in chronic conditions, remain unknown. Here, we characterize the “anergic” phenotype and demonstrate functional, transcriptional, and phenotypic similarities to the “exhausted” state in tumor-infiltrating NK cells. Furthermore, we identify zinc finger transcription factor Egr2 and diacylglycerol kinase DGKα as common negative regulators controlling NK cell dysfunction. Finally, experiments in a 3D organotypic spheroid culture model and an in vivo tumor model suggest that a nanoparticle-based delivery platform can reprogram these dysfunctional natural killer cell populations in their native microenvironment. This approach may become clinically relevant for the development of novel anti-tumor immunotherapeutic strategies.

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.

A transformable three-dimensional simulated solid tumor model reveals the widespread killing potential of natural killer cells with controlled lytic granule positioning

Abstract Cancer immunotherapy using engineered natural killer (NK) cells has shown great promise. However, the limited spatial complexity of current models hinders the study of NK cells in three-dimensional, solid tumor-like environments. Previously, we found that NK cells converge lytic granules before degranulation. It helps focus the secretion of cytotoxic cargos to the synaptic cleft, thus preventing the non-specific killing of bystander cells. We had speculated that bypassing this protective mechanism and forcing NK cells to degranulate non-directionally may promote broader destruction of cancer cells and eradicate tumor-resident non-triggering cells. To evaluate our hypothesis, we designed a novel strategy for creating complex cellular environments with controlled spatial distribution and intercellular dynamics. Using hydrogel-embedded cells as building blocks, we construct 3D models that arrange multiple cell populations within desired inner structures. Notably, these structures can undergo controlled transformations enabled by hydrogels comprised of thermo-responsive polymers. During this transformation, cells experienced rapid but mechanically gentle translocation to pre-designated positions, allowing us to control cell contacts actively. With these systems (which we have termed TheCOS for Thermal Collapse Of Strata), we observed that controlling NK cell lytic granule positioning at a lytic immune synapse was able to promote bystander cell death within a complex multicellular environment. Using quantitative imaging, we calculated an area of damage attributable to radial degranulation, which suggests a potential benefit to this as a strategy for improving cytotoxic cell therapy for solid tumors.

Exploring the effect of polyamines on NK cell function in colorectal cancer process based on glycolysis

Natural killer (NK) cells are lymphocytes with important anti-tumour functions. Cellular metabolism is dynamically regulated in NK cells and strongly influences their responses. Myc is a key regulator of immune cell activity and function, but little is known about how Myc controls NK cell activation and function. In this study, we found that c-Myc is involved in the regulation of NK cell immune activity. In the development of colon cancer, the energy generation disorder of tumor cells promotes the plunder of polyamines of NK cells by tumor cells, resulting in the inhibition of NK cell c-Myc. After inhibition of c-Myc, glycolysis of NK cells was impaired, resulting in decreased killing activity. There are three main types of polyamines: putrescine (Put), spermidine (Spd) and spermine (Spm). We found that the NK cells could reverse the inhibition state of c-Myc and glycolysis energy supply disorder and recover the killing activity of NK cells after giving certain spermidine. These results suggest that polyamine content and glycolysis supply under the regulation of c-Myc play a crucial role in the immune activity of NK cells.

Disturbed natural killer cell homeostasis in the salivary gland enhances autoimmune pathology via IFN-γ in a mouse model of primary Sjögren’s syndrome

Innate lymphoid cells (ILCs), including natural killer (NK) cells, ILC1, ILC2, lymphoid tissue-inducer (LTi) cells, and ILC3 cell, play a key role in various immune responses. Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by chronic inflammation of exocrine glands, such as the lacrimal and salivary glands (SGs). The role of NK cells among ILCs in the pathogenesis of pSS is still unclear. In this study, the characteristics and subsets of NK cells in the salivary gland (SG) tissue were analyzed using a murine model of pSS. Multiple phenotypes and cytotoxic signature of the SG NK cells in control and pSS model mice were evaluated by flow cytometric analysis. Intracellular expression of interferon-γ (IFN-γ) among T cells and NK cells from the SG tissues was compared by in vitro experiments. In addition, pathological analysis was performed using anti-asialo-GM1 (ASGM1) antibody (Ab)-injected pSS model mice. The number of conventional NK (cNK) cells in the SG of pSS model mice significantly increased compared with that in control mice at 6 weeks of age. The production level of IFN-γ was significantly higher in SG NK cells than in SG T cells. The depletion of NK cells by ASGM1 Ab altered the ratio of tissue resident NK (rNK) cells to cNK cells, which inhibited the injury to SG cells with the recovery of saliva secretion in pSS model mice. The results indicate that SG cNK cells may enhance the autoreactive response in the target organ by upregulating of IFN-γ, whereas SG rNK cells protect target cells against T cell cytotoxicity. Therefore, the activation process and multiple functions of NK cells in the target organ could be helpful to develop potential markers for determining autoimmune disease activity and target molecules for incurable immune disorders.

Underlying mechanisms of evasion from NK cells as rationale for improvement of NK cell-based immunotherapies.

Natural killer (NK) cells belong to the family of innate immune cells with the capacity to recognize and kill tumor cells. Different phenotypes and functional properties of NK cells have been described in tumor patients, which could be shaped by the tumor microenvironment. The discovery of HLA class I-specific inhibitory receptors controlling NK cell activity paved the way to the fundamental concept of modulating immune responses that are regulated by an array of inhibitory receptors, and emphasized the importance to explore the potential of NK cells in cancer therapy. Although a whole range of NK cell-based approaches are currently being developed, there are still major challenges that need to be overcome for improved efficacy of these therapies. These include escape of tumor cells from NK cell recognition due to their expression of inhibitory molecules, immune suppressive signals of NK cells, reduced NK cell infiltration of tumors, an immune suppressive micromilieu and limited in vivo persistence of NK cells. Therefore, this review provides an overview about the NK cell biology, alterations of NK cell activities, changes in tumor cells and the tumor microenvironment contributing to immune escape or immune surveillance by NK cells and their underlying molecular mechanisms as well as the current status and novel aspects of NK cell-based therapeutic strategies including their genetic engineering and their combination with conventional treatment options to overcome tumor-mediated evasion strategies and improve therapy efficacy.

Abstract 2819: Suppression of NKG2A mediated inhibition in ex vivo expanded natural killer cells increases their cytotoxicity

Abstract In this study we propose to circumvent HLA-E/NKG2A mediated Natural Killer (NK) cell inhibition by suppression of NKG2A, to enhance cytotoxicity of ex vivo expanded NK cells. One mechanism employed by tumor cells to evade immunosurveillance is through induction of the surface expression of unconventional HLA ligands that agonize inhibitory receptors on immune cells. Specifically on some tumors, HLA-E is either expressed or its expression is known to be induced by IFNγ and is indicative of resistance to immunotherapy. HLA-E agonizes the CD94/NKG2A inhibitory complex on NK cells and some T cells to lessen their cytotoxicity, potentially decreasing the efficacy of cellular therapy with these immune cells. The CD94/NKG2A inhibitory complex is in balance with CD94/NKG2C stimulatory complex. HLA-E binds both of these complexes and the cytolytic activity of NK cells is influenced by the relative ratios of CD94 complexed to NKG2A or NKG2C. Thus, altering the ratio to increase NKG2C will increase NK cell cytotoxicity. In this study we show that NK cells ex vivo expanded with PM21-particle technology are highly cytotoxic and have elevated expression of NKG2A. These expanded NK cells also secrete high levels of IFNγ, inducing expression of HLA-E in tumor cells. To increase the cytotoxic potential of these ex vivo expanded NK cells, the potential to form CD94/NKG2A inhibitory complex was suppressed by either antibody blockade of NKG2A or deletion of the NKG2A gene by CRISPR/Cas9 editing. Cytotoxicity of NK cells against a lung cancer cell line stably expressing HLA-E were determined by kinetic live-cell imaging. Multiple NK cell:target (NK:T) ratios were used to show an increase in cytotoxicity over control NK cell conditions (alone or with isotype control) in the presence of NKG2A blocking antibodies with 39% increase observed at 1:10 NK:T ratio at 96h with anti-NKG2A and 56% increase with NKG2A knockout NK cells. These data suggest that blockade of CD94/NKG2A complex can improve cytotoxic activity of ex vivo expanded NK cells and could provide a promising effector population with the potential for enhanced therapeutic efficacy. Citation Format: Tayler J. Croom-Perez, Liza D. Robles-Carrillo, Thomas A. Dieffenthaller, Alicja J. Copik. Suppression of NKG2A mediated inhibition in ex vivo expanded natural killer cells increases their cytotoxicity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2819.

Natural Killer Cells in Antibody Independent and Antibody Dependent HIV Control.

Infection with the human immunodeficiency virus (HIV), when left untreated, typically leads to disease progression towards acquired immunodeficiency syndrome. Some people living with HIV (PLWH) control their virus to levels below the limit of detection of standard viral load assays, without treatment. As such, they represent examples of a functional HIV cure. These individuals, called Elite Controllers (ECs), are rare, making up <1% of PLWH. Genome wide association studies mapped genes in the major histocompatibility complex (MHC) class I region as important in HIV control. ECs have potent virus specific CD8+ T cell responses often restricted by protective MHC class I antigens. Natural Killer (NK) cells are innate immune cells whose activation state depends on the integration of activating and inhibitory signals arising from cell surface receptors interacting with their ligands on neighboring cells. Inhibitory NK cell receptors also use a subset of MHC class I antigens as ligands. This interaction educates NK cells, priming them to respond to HIV infected cell with reduced MHC class I antigen expression levels. NK cells can also be activated through the crosslinking of the activating NK cell receptor, CD16, which binds the fragment crystallizable portion of immunoglobulin G. This mode of activation confers NK cells with specificity to HIV infected cells when the antigen binding portion of CD16 bound immunoglobulin G recognizes HIV Envelope on infected cells. Here, we review the role of NK cells in antibody independent and antibody dependent HIV control.

Individualized Constellation of Killer Cell Immunoglobulin-Like Receptors and Cognate HLA Class I Ligands that Controls Natural Killer Cell Antiviral Immunity Predisposes COVID-19.

Background: The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection causes coronavirus disease-2019 (COVID-19) in some individuals, while the majority remain asymptomatic. Natural killer (NK) cells play an essential role in antiviral defense. NK cell maturation and function are regulated mainly by highly polymorphic killer cell immunoglobulin-like receptors (KIR) and cognate HLA class I ligands. Herein, we tested our hypothesis that the individualized KIR and HLA class I ligand combinations that control NK cell function determine the outcome of SARS-CoV-2 infection. Methods: We characterized KIR and HLA genes in 200 patients hospitalized for COVID-19 and 195 healthy general population controls. Results: The KIR3DL1+HLA-Bw4+ [Odds ratio (OR) = 0.65, p = 0.03] and KIR3DL2+HLA-A3/11+ (OR = 0.6, p = 0.02) combinations were encountered at significantly lower frequency in COVID-19 patients than in the controls. Notably, 40% of the patients lacked both of these KIR+HLA+ combinations compared to 24.6% of the controls (OR = 2.04, p = 0.001). Additionally, activating receptors KIR2DS1+KIR2DS5+ are more frequent in patients with severe COVID-19 than patients with mild disease (OR = 1.8, p = 0.05). Individuals carrying KIR2DS1+KIR2DS5+ genes but missing either KIR3DL1+HLA-Bw4+ combination (OR = 1.73, p = 0.04) or KIR3DL2+HLA-A3/11+ combination (OR = 1.75, p = 0.02) or both KIR3DL1+HLA-Bw4+ and KIR2DL2+HLA-A3/11+ combinations (OR = 1.63, p = 0.03) were more frequent in the COVID-19 cohort compared to controls. Conclusions: The absence of KIR3DL1+HLA-Bw4+ and KIR3DL2+HLA-A3/11+ combinations presumably yields inadequate NK cell maturation and reduces anti-SARS-CoV-2 defense, causing COVID-19. An increased frequency of KIR2DS1+KIR2DS5+ in severe COVID-19 patients suggests vigorous NK cell response triggered via these activating receptors and subsequent production of exuberant inflammatory cytokines responsible for severe COVID-19. Our results demonstrate that specific KIR-HLA combinations that control NK cell maturation and function are underlying immunogenetic variables that determine the dual role of NK cells in mediating beneficial antiviral and detrimental pathologic action. These findings offer a framework for developing potential host genetic biomarkers to distinguish individuals prone to COVID-19.

Contribution of Natural Killer cells to HIV control in Elite Controllers

Untreated HIV infection usually leads to disease progression and development of the acquired immunodeficiency syndrome. A rare subset of people living with HIV control HIV without anti-retroviral therapy. These individuals, known as Elite Controllers (ECs), represent examples of a functional HIV cure. ECs differ from non-controllers is many aspects. Some are infected with defective virus, most have potent CD4 and CD8 virus-specific T cell responses and proviruses in these individuals tend to be inserted into regions with characteristics of deep latency. Natural Killer (NK) cells are innate immune cells that function at the intersection of innate and adaptive immunity. They have the capacity to recognize and respond to HIV-infected cells from the earliest stages in infection. NK cells can be activated through antibody independent and antibody dependent mechanisms to elicit functions that control HIV and kill infected cells. This manuscript will review the role of NK cells in HIV control.

Echinacea purpurea Extract Enhances Natural Killer Cell Activity In Vivo by Upregulating MHC II and Th1-type CD4+ T Cell Responses.

There are a number of factors that cause immune system disruption, including infection caused by foreign antigens and decreased immunity due to excessive exercise, and public interest in improving immunity is growing. In this study, we investigate the immunomodulatory effects of Echinacea purpurea (E) extract in C57BL/6N mice that were exposed to a forced swimming exercise. There were six experimental groups as follows: wild-type, forced swimming exercise control, positive control (red ginseng, 300 mg/kg), and E (50, 100, and 200 mg/kg b.w.) groups. The mice were administered the E extract for 2 weeks. We detected chicoric acid, the active substance of E, through high-performance liquid chromatography and evaluated changes in the following laboratory values in response to forced swimming exercise using flow cytometry and ELISA: the major histocompatibility complex (MHC), CD4+ and CD8+ T cells, Th1 and Th2 cytokines, natural killer (NK) cell activity, and number of leukocytes. Oral E intake increased levels of MHC II, CD4+ T cells, Th1 cytokines, and NK cell activity. In addition, E treatment increased B cell proliferation, leukocyte counts, and immunoglobulin levels. Taken together, these results suggest that the chicoric acid of E can improve immune response by controlling NK cell activity, which may be a useful function for immunomodulation systems.

Exploring natural killer cell immunology as a therapeutic strategy in lung cancer.

Cytotoxic immune cells are key in the control of tumor development and progression. Natural killer (NK) cells are the cytotoxic arm of the innate immune system with the capability to kill tumor cells and surveil tumor cell dissemination. As such, the interest in harnessing NK cells in tumor control is increasing in many solid tumor types, including lung cancer. Here, we review the pre-clinical models used to unveil the role of NK cells in immunosurveillance of solid tumors and highlight measures to enhance NK cell activity. Importantly, the development of NK immunotherapy is rapidly evolving. Enhancing the NK cell response can be achieved using two broad modalities: enhancing endogenous NK cell activity, or performing adoptive transfer of pre-activated NK cells to patients. Numerous clinical trials are evaluating the efficacy of NK cell immunotherapy in isolation or in combination with standard treatments, with encouraging initial results. Pre-clinical studies and early phase clinical trials suggest that patients with solid tumors, including lung cancer, have the potential to benefit from recent developments in NK cell immunotherapy.

Fatty acid-binding protein 5 controls lung tumor metastasis by regulating the maturation of natural killer cells in the lung.

Fatty acid-binding protein (FABP) 5 is highly expressed in various types of tumors and is strongly correlated with tumor growth, development, and metastasis. However, it is unclear how the expression of FABP5 in the host affects tumor progression. In this study, using a lung tumor metastasis model in mice, we found that FABP5-deficient mice were more susceptible to tumor metastasis, which is accompanied by infiltration of a lower frequency of activated natural killer (NK) cells in the lung. Additionally, FABP5 deficiency leads to impaired maturation of NK cells in the lungs, but not in the bone marrow and spleen. Taken together, our results provide the first evidence that FABP5 in the host regulates lung tumor metastasis through controlling NK cell maturation.

Selection of allogeneic hematopoietic cell transplant donors to optimize natural killer cell alloreactivity

Natural killer (NK) cells are potent mediators of the graft versus leukemia phenomenon critical to the success of allogeneic hematopoietic cell transplantation. Central to calibrating NK effector function via their interaction with class I human leukocyte antigens are the numerous inhibitory killer Ig-like receptors (KIR). The KIR receptors are encoded by a family of polymorphic genes, whose expression is largely stochastic and uninfluenced by human leukocyte antigens genotype. These features provide the opportunity to select hematopoietic cell donors with favorable KIR genotypes that confer enhanced protection from relapse via NK-mediated graft versus leukemia. Over the last 2 decades, a large body of work has emerged examining the use of KIR genotyping to stratify potential donors based on anticipated NK alloreactivity. Overall, these results support KIR-based donor selection for patients undergoing allogeneic hematopoietic cell transplantation for a diagnosis of acute myelogenous leukemia. Despite this, the underlying factors that control NK cell responsiveness are not completely understood, and opportunities remain to refine donor selection using NK cell receptor genotyping. In this review, we will summarize the relevant findings with respect to KIR genotyping as a selection parameter for allogeneic hematopoietic cell donors and address practical considerations with respect to KIR-based selection of donors for patients with myeloid neoplasia.

Landscape and Dynamics of the Transcriptional Regulatory Network During Natural Killer Cell Differentiation

Natural killer (NK) cells are essential in controlling cancer and infection. However, little is known about the dynamics of the transcriptional regulatory machinery during NK cell differentiation. In this study, we applied the assay of transposase accessible chromatin with sequencing (ATAC-seq) technique in a home-developed in vitro NK cell differentiation system. Analysis of ATAC-seq data illustrated two distinct transcription factor (TF) clusters that dynamically regulate NK cell differentiation. Moreover, two TFs from the second cluster, FOS-like 2 (FOSL2) and early growth response 2 (EGR2), were identified as novel essential TFs that control NK cell maturation and function. Knocking down either of these two TFs significantly impacted NK cell differentiation. Finally, we constructed a genome-wide transcriptional regulatory network that provides a better understanding of the regulatory dynamics during NK cell differentiation.

The cancer-natural killer cell immunity cycle.

Immunotherapy with checkpoint blockade induces rapid and durable immune control of cancer in some patients and has driven a monumental shift in cancer treatment. Neoantigen-specific CD8+ T cells are at the forefront of current immunotherapy strategies, and the majority of drug discovery and clinical trials revolve around further harnessing these immune effectors. Yet the immune system contains a diverse range of antitumour effector cells, and these must function in a coordinated and synergistic manner to overcome the immune-evasion mechanisms used by tumours and achieve complete control with tumour eradication. A key antitumour effector is the natural killer (NK) cells, cytotoxic innate lymphocytes present at high frequency in the circulatory system and identified by their exquisite ability to spontaneously detect and lyse transformed or stressed cells. Emerging data show a role for intratumoural NK cells in driving immunotherapy response and, accordingly, there have been renewed efforts to further elucidate and target the pathways controlling NK cell antitumour function. In this Review, we discuss recent clinical evidence that NK cells are a key immune constituent in the protective antitumour immune response and highlight the major stages of the cancer-NK cell immunity cycle. We also perform a new analysis of publicly available transcriptomic data to provide an overview of the prognostic value of NK cell gene expression in 25 tumour types. Furthermore, we discuss how the role of NK cells evolves with tumour progression, presenting new opportunities to target NK cell function to enhance cancer immunotherapy response rates across a more diverse range of cancers.

Targeting NK Cell Checkpoint Receptors or Molecules for Cancer Immunotherapy.

Checkpoint blockade therapy, for example using antibodies against CTLA-4 and PD-1/PD-L1, relieves T cells from the suppression by inhibitory checkpoints in the tumor microenvironment; thereby achieving good outcomes in the treatment of different cancer types. Like T cells, natural killer (NK) cell inhibitory receptors function as checkpoints for NK cell activation. Upon interaction with their cognate ligands on infected cells, tumor cells, dendritic cells and regulatory T cells, signals from these receptors severely affect NK cells' activation and effector functions, resulting in NK cell exhaustion. Checkpoint inhibition with antagonistic antibodies (Abs) can rescue NK cell exhaustion and arouse their robust anti-tumor capacity. Most notably, the response to anti-PD-1 therapy can be enhanced by the increased frequency and activation of NK cells, thereby increasing the overall survival of patients with multiple types of cancer. In addition, rescue of NK cell activity could enhance adaptive T cells' anti-tumor activity. Some antagonistic Abs (e.g., anti-TIGIT and anti-NKG2A monoclonal Abs) have extraordinary potential in cancer therapy, as evidenced by their induction of potent anti-tumor immunity through recovering both NK and T cell function. In this review, we summarize the dysfunction of NK cells in the tumor microenvironment and the key NK cell checkpoint receptors or molecules that control NK cell function. We particularly focus on recent advances in the most promising strategies through blockade of NK cell checkpoints or their combination with other approaches to more effectively reject tumors.

Highly efficient serum-free manipulation of miRNA in human NK cells without loss of viability or phenotypic alterations is accomplished with TransIT-TKO.

Natural killer (NK) cells are innate lymphocytes with functions that include target cell killing, inflammation and regulation. NK cells integrate incoming activating and inhibitory signals through an array of germline-encoded receptors to gauge the health of neighbouring cells. The reactive potential of NK cells is influenced by microRNA (miRNA), small non-coding sequences that interfere with mRNA expression. miRNAs are highly conserved between species, and a single miRNA can have hundreds to thousands of targets and influence entire cellular programs. Two miRNA species, miR-155-5p and miR-146a-5p are known to be important in controlling NK cell function, but research to best understand the impacts of miRNA species within NK cells has been bottlenecked by a lack of techniques for altering miRNA concentrations efficiently and without off-target effects. Here, we describe a non-viral and straightforward approach for increasing or decreasing expression of miRNA in primary human NK cells. We achieve >90% transfection efficiency without off-target impacts on NK cell viability, education, phenotype or function. This opens the opportunity to study and manipulate NK cell miRNA profiles and their impacts on NK cellular programs which may influence outcomes of cancer, inflammation and autoimmunity.

Recalling the Biological Significance of Immune Checkpoints on NK Cells: A Chance to Overcome LAG3, PD1, and CTLA4 Inhibitory Pathways by Adoptive NK Cell Transfer?

Immune checkpoint receptors (IC) positively or negatively regulate the activation of the host immune response, preventing unwanted reactions against self-healthy tissues. In recent years the term IC has been mainly used for the inhibitory ICs, which are critical to control Natural Killer (NK) and Cytotoxic CD8+ T cells due to its high cytotoxic potential. Due to the different nature of the signals that regulate T and NK cell activation, specific ICs have been described that mainly regulate either NK cell or T cell activity. Thus, strategies to modulate NK cell activity are raising as promising tools to treat tumors that do not respond to T cell-based immunotherapies. NK cell activation is mainly regulated by ICs and receptors from the KIR, NKG2 and NCRs families and the contribution of T cell-related ICs is less clear. Recently, NK cells have emerged as contributors to the effect of inhibitors of T cell-related ICs like CTLA4, LAG3 or the PD1/PD-L1 axes in cancer patients, suggesting that these ICs also regulate the activity of NK cells under pathological conditions. Strikingly, in contrast to NK cells from cancer patients, the level of expression of these ICs is low on most subsets of freshly isolated and in vitro activated NK cells from healthy patients, suggesting that they do not control NK cell tolerance and thus, do not act as conventional ICs under non-pathological conditions. The low level of expression of T cell-related ICs in “healthy” NK cells suggest that they should not be restricted to the detrimental effects of these inhibitory mechanisms in the cancer microenvironment. After a brief introduction of the regulatory mechanisms that control NK cell anti-tumoral activity and the conventional ICs controlling NK cell tolerance, we will critically discuss the potential role of T cell-related ICs in the control of NK cell activity under both physiological and pathological (cancer) conditions. This discussion will allow to comprehensively describe the chances and potential limitations of using allogeneic NK cells isolated from a healthy environment to overcome immune subversion by T cell-related ICs and to improve the efficacy of IC inhibitors (ICIs) in a safer way.

Single-cell transcriptomics of the naked mole-rat reveals unexpected features of mammalian immunity.

The immune system comprises a complex network of specialized cells that protects against infection, eliminates cancerous cells, and regulates tissue repair, thus serving a critical role in homeostasis, health span, and life span. The subterranean-dwelling naked mole-rat (NM-R; Heterocephalus glaber) exhibits prolonged life span relative to its body size, is unusually cancer resistant, and manifests few physiological or molecular changes with advancing age. We therefore hypothesized that the immune system of NM-Rs evolved unique features that confer enhanced cancer immunosurveillance and prevent the age-associated decline in homeostasis. Using single-cell RNA-sequencing (scRNA-seq) we mapped the immune system of the NM-R and compared it to that of the short-lived, cancer-prone mouse. In contrast to the mouse, we find that the NM-R immune system is characterized by a high myeloid-to-lymphoid cell ratio that includes a novel, lipopolysaccharide (LPS)-responsive, granulocyte cell subset. Surprisingly, we also find that NM-Rs lack canonical natural killer (NK) cells. Our comparative genomics analyses support this finding, showing that the NM-R genome lacks an expanded gene family that controls NK cell function in several other species. Furthermore, we reconstructed the evolutionary history that likely led to this genomic state. The NM-R thus challenges our current understanding of mammalian immunity, favoring an atypical, myeloid-biased mode of innate immunosurveillance, which may contribute to its remarkable health span.