CD160 is essential for NK-mediated IFN-γ production

Aberrant Expressions of Co-stimulatory and Co-inhibitory Molecules in Autoimmune Diseases

Co-signaling molecules include co-stimulatory and co-inhibitory molecules and play important roles in modulating immune responses. The roles of co-signaling molecules in autoimmune diseases have not been clearly defined. We assessed the expressions of co-stimulatory and co-inhibitory molecules in autoimmune diseases through a bioinformatics-based study. By using datasets of whole-genome transcriptome, the expressions of 54 co-stimulatory or co-inhibitory genes in common autoimmune diseases were analyzed using Robust rank aggregation (RRA) method. Nineteen array datasets and 6 RNA-seq datasets were included in the RRA discovery study and RRA validation study, respectively. Significant genes were further validated in several autoimmune diseases including Graves' disease (GD). RRA discovery study suggested that CD160 was the most significant gene aberrantly expressed in autoimmune diseases (Adjusted P = 5.9E-12), followed by CD58 (Adjusted P = 5.7E-06) and CD244 (Adjusted P = 9.5E-05). RRA validation study also identified CD160 as the most significant gene aberrantly expressed in autoimmune diseases (Adjusted P = 5.9E-09). We further found that the aberrant expression of CD160 was statistically significant in multiple autoimmune diseases including GD (P < 0.05), and CD160 had a moderate role in diagnosing those autoimmune diseases. Flow cytometry confirmed that CD160 was differentially expressed on the surface of CD8⁺ T cells between GD patients and healthy controls (P = 0.002), which proved the aberrant expression of CD160 in GD at the protein level. This study suggests that CD160 is the most significant co-signaling gene aberrantly expressed in autoimmune diseases. Treatment strategy targeting CD160-related pathway may be promising for the therapy of autoimmune diseases.

Activated and Exhausted MAIT Cells Foster Disease Progression and Indicate Poor Outcome in Hepatocellular Carcinoma

PURPOSE

Innate immunity is an indispensable arm of tumor immune surveillance, and the liver is an organ with a predominance of innate immunity, where mucosal-associated invariant T (MAIT) cells are enriched. However, little is known about the phenotype, functions, and immunomodulatory role of MAIT cells in hepatocellular carcinoma (HCC).Experimental Design: The distribution, phenotype, and function of MAIT cells in patients with HCC were evaluated by both flow cytometry (FCM) and in vitro bioassays. Transcriptomic analysis of MAIT cells was also performed. Prognostic significance of tumor-infiltrating MAIT cells was validated in four independent cohorts of patients with HCC.

RESULTS

Despite their fewer densities in HCC tumor than normal liver, MAIT cells were significantly enriched in the HCC microenvironment compared with other mucosa-associated organs. Tumor-derived MAIT cells displayed a typical CCR7^-CD45RA^-CD45RO⁺CD95⁺ effector memory phenotype with lower costimulatory and effector capabilities. Tumor-educated MAIT cells significantly upregulated inhibitory molecules like PD-1, CTLA-4, TIM-3, secreted significantly less IFNγ and IL17, and produced minimal granzyme B and perforin while shifting to produce tumor-promoting cytokines like IL8. Transcriptome sequencing confirmed that tumor-derived MAIT cells were reprogrammed toward a tumor-promoting direction by downregulating genes enriched in pathways of cytokine secretion and cytolysis effector function like NFKB1 and STAT5B and by upregulating genes like IL8, CXCL12, and HAVCR2 (TIM-3). High infiltration of MAIT cells in HCC significantly correlated with an unfavorable clinical outcome, revealed by FCM, qRT-PCR, and multiplex IHC analyses, respectively.

CONCLUSIONS

HCC-infiltrating MAIT cells were functionally impaired and even reprogrammed to shift away from antitumor immunity and toward a tumor-promoting direction.See related commentary by Carbone, p. 3199.

Signal Transduction Via Co-stimulatory and Co-inhibitory Receptors

T-cell receptor (TCR)-mediated antigen-specific stimulation is essential for initiating T-cell activation. However, signaling through the TCR alone is not sufficient for inducing an effective response. In addition to TCR-mediated signaling, signaling through antigen-independent co-stimulatory or co-inhibitory receptors is critically important not only for the full activation and functional differentiation of T cells but also for the termination and suppression of T-cell responses. Many studies have investigated the signaling pathways underlying the function of each molecular component. Co-stimulatory and co-inhibitory receptors have no kinase activity, but their cytoplasmic region contains unique functional motifs and potential phosphorylation sites. Engagement of co-stimulatory receptors leads to recruitment of specific binding partners, such as adaptor molecules, kinases, and phosphatases, via recognition of a specific motif. Consequently, each co-stimulatory receptor transduces a unique pattern of signaling pathways. This review focuses on our current understanding of the intracellular signaling pathways provided by co-stimulatory and co-inhibitory molecules, including B7:CD28 family members, immunoglobulin, and members of the tumor necrosis factor receptor superfamily.

HVEM network signaling in cancer

Somatic mutations in cancer cells may influence tumor growth, survival, or immune interactions in their microenvironment. The tumor necrosis factor receptor family member HVEM (TNFRSF14) is frequently mutated in cancers and has been attributed a tumor suppressive role in some cancer contexts. HVEM functions both as a ligand for the lymphocyte checkpoint proteins BTLA and CD160, and as a receptor that activates NF-κB signaling pathways in response to BTLA and CD160 and the TNF ligands LIGHT and LTα. BTLA functions to inhibit lymphocyte activation, but has also been ascribed a role in stimulating cell survival. CD160 functions to co-stimulate lymphocyte function, but has also been shown to activate inhibitory signaling in CD4⁺ T cells. Thus, the role of HVEM within diverse cancers and in regulating the immune responses to these tumors is likely context specific. Additionally, development of therapeutics that target proteins within this network of interacting proteins will require a deeper understanding of how these proteins function in a cancer-specific manner. However, the prominent role of the HVEM network in anti-cancer immune responses indicates a promising area for drug development.

Herpes Simplex Virus 1 Latency and the Kinetics of Reactivation Are Regulated by a Complex Network of Interactions between the Herpesvirus Entry Mediator, Its Ligands (gD, BTLA, LIGHT, and CD160), and the Latency-Associated Transcript

Recently, we reported that the herpesvirus entry mediator (HVEM; also called TNFRSF14 or CD270) is upregulated by the latency-associated transcript (LAT) of herpes simplex virus 1 (HSV-1) and that the absence of HVEM affects latency reactivation but not primary infection in ocularly infected mice. gD has been shown to bind to HVEM. LIGHT (TNFSF14), CD160, and BTLA (B- and T-lymphocyte attenuator) also interact with HVEM and can interfere with HSV gD binding. It was not known if LIGHT, CD160, or BTLA affected the level of latency reactivation in the trigeminal ganglia (TG) of latently infected mice. To address this issue, we ocularly infected LIGHT^-/-, CD160^-/-, and BTLA^-/- mice with LAT(+) and LAT(-) viruses, using similarly infected wild-type (WT) and HVEM^-/- mice as controls. The amount of latency, as determined by the levels of gB DNA in the TG of the LIGHT^-/-, CD160^-/-, and BTLA^-/- mice infected with either LAT(+) or LAT(-) viruses, was lower than that in WT mice infected with LAT(+) virus and was similar in WT mice infected with LAT(-) virus. The levels of LAT RNA in HVEM^-/-, LIGHT^-/-, CD160^-/-, and BTLA^-/- mice infected with LAT(+) virus were similar and were lower than the levels of LAT RNA in WT mice. However, LIGHT^-/-, CD160^-/-, and BTLA^-/- mice, independent of the presence of LAT, had levels of reactivation similar to those of WT mice infected with LAT(+) virus. Faster reactivation correlated with the upregulation of HVEM transcript. The LIGHT^-/-, CD160^-/-, and BTLA^-/- mice had higher levels of HVEM expression, and this, along with the absence of BTLA, LIGHT, or CD160, may contribute to faster reactivation, while the absence of each molecule, independent of LAT, may have contributed to lower latency. This study suggests that, in the absence of competition with gD for binding to HVEM, LAT RNA is important for WT levels of latency but not for WT levels of reactivation.IMPORTANCE The effects of BTLA, LIGHT, and CD160 on latency reactivation are not known. We show here that in BTLA, LIGHT, or CD160 null mice, latency is reduced; however, HVEM expression is upregulated compared to that of WT mice, and this upregulation is associated with higher reactivation that is independent of LAT but dependent on gD expression. Thus, one of the mechanisms by which BTLA, LIGHT, and CD160 null mice enhance reactivation appears to be the increased expression of HVEM in the presence of gD. Thus, our results suggest that blockade of HVEM-LIGHT-BTLA-CD160 contributes to reduced HSV-1 latency and reactivation.

HVEM and CD160: Regulators of Immunopathology During Malaria Blood-Stage

CD8⁺ T cells are key players during infection with the malaria parasite Plasmodium berghei ANKA (PbA). While they cannot provide protection against blood-stage parasites, they can cause immunopathology, thus leading to the severe manifestation of cerebral malaria. Hence, the tight control of CD8⁺ T cell function is key in order to prevent fatal outcomes. One major mechanism to control CD8⁺ T cell activation, proliferation and effector function is the integration of co-inhibitory and co-stimulatory signals. In this study, we show that one such pathway, the HVEM-CD160 axis, significantly impacts CD8⁺ T cell regulation and thereby the incidence of cerebral malaria. Here, we show that the co-stimulatory molecule HVEM is indeed required to maintain CD8⁺ T effector populations during infection. Additionally, by generating a CD160^-/- mouse line, we observe that the HVEM ligand CD160 counterbalances stimulatory signals in highly activated and cytotoxic CD8⁺ T effector cells, thereby restricting immunopathology. Importantly, CD160 is also induced on cytotoxic CD8⁺ T cells during acute Plasmodium falciparum malaria in humans. In conclusion, CD160 is specifically expressed on highly activated CD8⁺ T effector cells that are harmful during the blood-stage of malaria.

Ox40 regulates the conversion and suppressive function of double-negative regulatory T cells

Naïve CD4 T cells can be converted to double-negative regulatory T cells (DNT) by mature dendritic cells (mDCs) and IL-2 stimulation, with IL-2 enhancing the proliferation and Perforin expression of DNT. However, the molecules that affect the conversion of DNT are still not clear. Here, we investigated the effects of Ox40 on the conversion and function of DNT in vitro and in vivo without IL-2. We found that OX86 (an Ox40 agonist) increased the conversion rate of DNT but failed to enhance the suppressive function of DNT. Ox40 deficiency profoundly decreased the conversion rate and suppressive function of DNT. This suppression decline was caused by effects of Ox40 on proliferation and apoptosis independent of Perforin, Granzyme B and Fas ligand. Ox40 deficiency influenced the regulatory function of DNT through multiple signals, such as Cxcr3, Cd160 and Cd30, independently of Prf, Gzmb and Fasl. In conclusion, we elucidated that Ox40 promotes the conversion and maintenance of DNT. Ox40 deficiency reduced the regulatory function of DNT both in vitro and in vivo by regulating proliferation, apoptosis, and suppression-related genes.

Reduced CD160 Expression Contributes to Impaired NK-cell Function and Poor Clinical Outcomes in Patients with HCC

: We previously reported that deficiencies in natural killer (NK)-cell number and function play an important role in the progression of hepatocellular carcinoma (HCC). However, the mechanisms underlying this phenomenon remain obscure. In this study, we analyzed the expression of CD160 on intrahepatic NK cells by evaluating peritumoral and intratumoral tissues of 279 patients with HCC and 20 healthy livers. We observed reduced expression of CD160 on intratumoral NK cells, and patients with lower CD160 cell densities within tumors exhibited worse disease and a higher recurrence rate. High-resolution microarray and gene set enrichment analysis of flow cytometry-sorted primary intrahepatic CD160⁺ and CD160^- NK cells of healthy livers indicated that human CD160⁺ NK cells exhibited functional activation, high IFNγ production, and NK-mediated immunity. In addition, global transcriptomic analysis of sorted peritumoral and intratumoral CD160⁺ NK cells revealed that intratumoral CD160⁺ NK cells are more exhausted than peritumoral CD160⁺ NK cells and produce less IFNγ. High levels of TGFβ1 interfered with production of IFNγ by CD160⁺ NK cells, blocking of which specifically restored IFNγ production in CD160⁺ NK cells to normal levels. These findings indicate that reduced numbers of CD160⁺ NK cells, together with the functional impairment of CD160⁺ NK cells by TGFβ1, contribute to tumor immune escape. In addition, restoring the expression of CD160 and blocking TGFβ1 appear a promising therapeutic strategy against liver cancer. SIGNIFICANCE: These findings show that reduced number and function of CD160⁺ NK cells in the tumor microenvironment contributes to immune escape of HCC; blocking TGFβ1 restores IFNγ production of CD160⁺ NK cells.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/23/6581/F1.large.jpg.

Tumor Necrosis Factor Receptor Superfamily in T Cell Priming and Effector Function

The tumor necrosis factor receptor superfamily (TNFRSF) and their ligands mediate lymphoid tissue development and homeostasis in addition to key aspects of innate and adaptive immune responses. T cells of the adaptive immune system express a number of TNFRSF members that are used to receive signals at different instructive stages and produce several tumor necrosis factor superfamily (TNFSF) members as effector molecules. There is also one example of a TNFRSF member serving as a ligand for negative regulatory checkpoint receptors. In most cases, the ligands in afferent and efferent phases are membrane proteins and thus the interaction with TNFRSF members must take place in immunological synapses and other modes of cell-cell interaction. A particular feature of the TNFRSF-mediated signaling is the prominent use of linear ubiquitin chains as scaffolds for signaling complexes that activate nuclear factor κ-B and Fos/Jun transcriptional regulators. This review will focus on the signaling mechanisms triggered by TNFRSF members in their role as costimulators of early and late phases of T cell instruction and the delivery mechanism of TNFSF members through the immunological synapses of helper and cytotoxic effector cells.

CD160 Stimulates CD8+ T Cell Responses and Is Required for Optimal Protective Immunity to Listeria monocytogenes

CD160 promotes NK cell cytotoxicity and IFN-γ production, but the function of CD160 on CD8⁺ T cells remains unclear with some studies supporting a coinhibitory role and others a costimulatory role. In this study, we demonstrate that CD160 has a costimulatory role in promoting CD8⁺ T cell effector functions needed for optimal clearance of oral Listeria monocytogenes infection. CD160^-/- mice did not clear oral L. monocytogenes as efficiently as wild type (WT) littermates. WT RAG^-/- and CD160^-/- RAG^-/- mice similarly cleared L. monocytogenes, indicating that CD160 on NK cells does not contribute to impaired L. monocytogenes clearance. Defective L. monocytogenes clearance is due to compromised intraepithelial lymphocytes and CD8⁺ T cell functions. There was a reduction in the frequencies of granzyme B-expressing intraepithelial lymphocytes in L. monocytogenes-infected CD160^-/- mice as compared with WT littermate controls. Similarly, the frequencies of granzyme B-expressing splenic CD8⁺ T cells and IFN-γ and TNF-α double-producer CD8⁺ T cells were significantly reduced in L. monocytogenes-infected CD160^-/- mice compared with WT littermates. Adoptive transfer studies showed that RAG^-/- recipients receiving CD160^-/- CD8⁺ T cells had a higher mortality, exhibited more weight loss, and had a higher bacterial burden compared with RAG^-/- recipients receiving WT CD8⁺ T cells. These findings demonstrate that CD160 provides costimulatory signals to CD8⁺ T cells needed for optimal CD8⁺ T cell responses and protective immunity during an acute mucosal bacterial infection.

LIGHT-HVEM Signaling in Innate Lymphoid Cell Subsets Protects Against Enteric Bacterial Infection

Innate lymphoid cells (ILCs) are important regulators of early infection at mucosal barriers. ILCs are divided into three groups based on expression profiles, and are activated by cytokines and neuropeptides. Yet, it remains unknown if ILCs integrate other signals in providing protection. We show that signaling through herpes virus entry mediator (HVEM), a member of the tumor necrosis factor (TNF) receptor superfamily, in ILC3 is important for host defense against oral infection with the bacterial pathogen Yersinia enterocolitica. HVEM stimulates protective interferon-γ (IFN-γ) secretion from ILCs, and mice with HVEM-deficient ILC3 exhibit reduced IFN-γ production, higher bacterial burdens and increased mortality. In addition, IFN-γ production is critical as adoptive transfer of wild-type but not IFN-γ-deficient ILC3 can restore protection to mice lacking ILCs. We identify the TNF superfamily member, LIGHT, as the ligand inducing HVEM signals in ILCs. Thus HVEM signaling mediated by LIGHT plays a critical role in regulating ILC3-derived IFN-γ production for protection following infection. VIDEO ABSTRACT.

Impact of benznidazole treatment on the functional response of Trypanosoma cruzi antigen-specific CD4+CD8+ T cells in chronic Chagas disease patients

Background

Chagas disease is caused by Trypanosoma cruzi. The persistence of the parasite is associated with the disease chronicity and the impairment of the cellular immune response. It has been reported that the CD4⁺CD8⁺ T cell population expands in chronic Chagas disease patients. Few studies have focused on this subset of cells, and very little is known about the impact of antiparasitic treatment on this population.

Methodology

Thirty-eight chronic Chagas disease patients (20 asymptomatic and 18 symptomatic) and twelve healthy controls were enrolled in this study. Peripheral blood mononuclear cells were stimulated with soluble T. cruzi antigens to analyze the production of cytokines and cytotoxic molecules by CD4⁺CD8⁺ T cells before and after benznidazole treatment. Additionally, expression and co-expression of five inhibitory receptors in these patients after treatment were studied using a multiparameter flow cytometry technique.

Principal findings

The frequency of CD4⁺CD8⁺ T cells was higher in chronic Chagas disease patients compared with healthy donors. Furthermore, a higher ratio of CD4⁺CD8^low/CD4⁺CD8^high subpopulations was observed in chronic Chagas disease patients than in healthy donors. Additionally, CD4⁺CD8⁺ T cells from these patients expressed and co-expressed higher levels of inhibitory receptors in direct proportion to the severity of the pathology. Benznidazole treatment reduced the frequency of CD4⁺CD8⁺ T cells and decreased the ratio of CD4⁺CD8^low/CD4⁺CD8^high subpopulations. The co-expression level of the inhibitory receptor was reduced after treatment simultaneously with the enhancement of the multifunctional capacity of CD4⁺CD8⁺ T cells. After treatment, an increase in the frequency of T. cruzi antigen-specific CD4⁺CD8⁺ T cells expressing IL-2 and TNF-α was also observed.

Conclusions

CD4⁺CD8⁺ T cells could play an important role in the control of T. cruzi infection since they were able to produce effector molecules for parasite control. Benznidazole treatment partially reversed the exhaustion process caused by T. cruzi infection in these cells with an improvement in the functional response of the T. cruzi antigen-specific CD4⁺CD8⁺ T cells.

Chagas disease is a neglected tropical disease caused by the intracellular parasite Trypanosoma cruzi. The persistence of the parasite leads to deterioration of the host immune response, which is known as an exhaustion process. This process affects T cell populations, leading to increased expression of inhibitory receptors that leads to a dysfunctional ability to respond to the parasite. CD4⁺CD8⁺ T cells form a poorly studied population of T cells in the context of Chagas disease. In this study, as in others previously reported, an increase in the frequency of these cells was observed in chronic Chagas disease patients. In addition, CD4⁺CD8⁺ T cells from chronic Chagas disease patients underwent stronger exhaustion processes with more severe disease pathology. A higher level of expression and co-expression of inhibitory receptors was observed in these cells in symptomatic compared with asymptomatic patients. Furthermore, we evaluated whether antiparasitic treatment affected the population of CD4⁺CD8⁺ T cells. Our results showed that after treatment, the functional capacity of these cells against the parasite improved. Concomitantly, a partial reversion of this exhaustion process occurred since the co-expression of inhibitory receptors decreased in CD4⁺CD8⁺ T cells from chronic patients after treatment.

NK-cell Editing Mediates Epithelial-to-Mesenchymal Transition via Phenotypic and Proteomic Changes in Melanoma Cell Lines

Tumor cell plasticity is a major obstacle for the cure of malignancies as it makes tumor cells highly adaptable to microenvironmental changes, enables their phenotype switching among different forms, and favors the generation of prometastatic tumor cell subsets. Phenotype switching toward more aggressive forms involves different functional, phenotypic, and morphologic changes, which are often related to the process known as epithelial-mesenchymal transition (EMT). In this study, we report natural killer (NK) cells may increase the malignancy of melanoma cells by inducing changes relevant to EMT and, more broadly, to phenotype switching from proliferative to invasive forms. In coculture, NK cells induced effects on tumor cells similar to those induced by EMT-promoting cytokines, including upregulation of stemness and EMT markers, morphologic transition, inhibition of proliferation, and increased capacity for Matrigel invasion. Most changes were dependent on the engagement of NKp30 or NKG2D and the release of cytokines including IFNγ and TNFα. Moreover, EMT induction also favored escape from NK-cell attack. Melanoma cells undergoing EMT either increased NK-protective HLA-I expression on their surface or downregulated several tumor-recognizing activating receptors on NK cells. Mass spectrometry-based proteomic analysis revealed in two different melanoma cell lines a partial overlap between proteomic profiles induced by NK cells or by EMT cytokines, indicating that various processes or pathways related to tumor progression are induced by exposure to NK cells.Significance: NK cells can induce prometastatic properties on melanoma cells that escape from killing, providing important clues to improve the efficacy of NK cells in innovative antitumor therapies. Cancer Res; 78(14); 3913-25. ©2018 AACR.

T-cell responses against CD19+ pediatric acute lymphoblastic leukemia mediated by bispecific T-cell engager (BiTE) are regulated contrarily by PD-L1 and CD80/CD86 on leukemic blasts

T-cell immunotherapies are promising options in relapsed/refractory B-precursor acute lymphoblastic leukemia (ALL). We investigated the effect of co-signaling molecules on T-cell attack against leukemia mediated by CD19/CD3-bispecific T-cell engager. Primary CD19+ ALL blasts (n≥10) and physiologic CD19+CD10+ bone marrow precursors were screened for 20 co-signaling molecules. PD-L1, PD-1, LAG-3, CD40, CD86, CD27, CD70 and HVEM revealed different stimulatory and inhibitory profiles of pediatric ALL compared to physiologic cells, with PD-L1 and CD86 as most prominent inhibitory and stimulatory markers. PD-L1 was increased in relapsed ALL patients (n=11) and in ALLs refractory to Blinatumomab (n=5). Exhaustion markers (PD-1, TIM-3) were significantly higher on patients' T cells compared to physiologic controls. T-cell proliferation and effector function was target-cell dependent and correlated to expression of co-signaling molecules. Blockade of inhibitory PD-1-PD-L and CTLA-4-CD80/86 pathways enhanced T-cell function whereas blockade of co-stimulatory CD28-CD80/86 interaction significantly reduced T-cell function. Combination of Blinatumomab and anti-PD-1 antibody was feasible and induced an anti-leukemic in vivo response in a 12-year-old patient with refractory ALL. In conclusion, ALL cells actively regulate T-cell function by expression of co-signaling molecules and modify efficacy of therapeutic T-cell attack against ALL. Inhibitory interactions of leukemia-induced checkpoint molecules can guide future T-cell therapies.

Mechanistic Sharing Between NK Cells in ABMR and Effector T Cells in TCMR

Human organ allograft rejection depends on effector lymphocytes: NK cells in antibody-mediated rejection (ABMR) and effector T cells in T cell-mediated rejection (TCMR). We hypothesized that NK cell CD16a stimulation and CD8 T cell TCR/CD3 stimulation represent highly similar effector systems, and should lead to shared molecular changes between ABMR and TCMR. We studied similarity between soluble proteins and the transcripts induced in CD16a stimulated NK cells and TCR/CD3-stimulated T cells in vitro. Of 30 soluble mediators tested, CD16a-activated NK cells and CD3/TCR activated T cells produced the same limited set of five mediators-CCL3, CCL4, CSF2, IFNG, and TNF-and failed to produce 25 others. Many transcripts increased in stimulated NK cells were also increased in CD3-stimulated CD8 T cells (FDR < 0.05), including IFNG, CSF2, CCL3, CCL4, and XCL1. We hypothesized that shared transcripts not produced by other cell types should be expressed both in ABMR and TCMR kidney transplant biopsies. CD160, XCL1, TNFRSF9, and IFNG were selective for TCR/CD3-activated T cells and CD16a-NK cells and all were strongly increased in ABMR and TCMR. The molecules such as CD160 and XCL1 shared between NK cells in ABMR and effector T cells in TCMR may hold insights into important rejection mechanisms.

A herpesvirus entry mediator mutein with selective agonist action for the inhibitory receptor B and T lymphocyte attenuator

The human cytomegalovirus opening reading frame UL144 is an ortholog of the TNF receptor superfamily member, herpesvirus entry mediator (HVEM; TNFRSF14). HVEM binds the TNF ligands, LIGHT and LTa; the immunoglobulin inhibitory receptor, B and T lymphocyte attenuator (BTLA); and the natural killer cell-activating receptor CD160. However, UL144 selectively binds BTLA, avoiding activation of inflammatory signaling initiated by CD160 in natural killer cells. BTLA and CD160 cross-compete for binding HVEM, but the structural basis for the ligand selectivity by UL144 and how it acts as an anti-inflammatory agonist remains unclear. Here, we modeled the UL144 structure and characterized its binding with BTLA. The UL144 structure was predicted to closely mimic the surface of HVEM, and we also found that both HVEM and UL144 bind a common epitope of BTLA, whether engaged in trans or in cis, that is shared with a BTLA antibody agonist. On the basis of the UL144 selectivity, we engineered a BTLA-selective HVEM protein to understand the basis for ligand selectivity and BTLA agonism to develop novel anti-inflammatory agonists. This HVEM mutein did not bind CD160 or TNF ligands but did bind BTLA with 10-fold stronger affinity than wild-type HVEM and retained potent inhibitory activity that reduced T-cell receptor, B-cell receptor, and interferon signaling in B cells. In conclusion, using a viral immune evasion strategy that shows broad immune-ablating activity, we have identified a novel anti-inflammatory BTLA-selective agonist.

The TNF Receptor Superfamily in Co-stimulating and Co-inhibitory Responses

Cytokines related to tumor necrosis factor (TNF) provide a communication network essential for coordinating multiple cell types into an effective host defense system against pathogens and malignant cells. The pathways controlled by the TNF superfamily differentiate both innate and adaptive immune cells and modulate stromal cells into microenvironments conducive to host defenses. Members of the TNF receptor superfamily activate diverse cellular functions from the production of type 1 interferons to the modulation of survival of antigen-activated T cells. Here, we focus attention on the subset of TNF superfamily receptors encoded in the immune response locus in chromosomal region 1p36. Recent studies have revealed that these receptors use diverse mechanisms to either co-stimulate or restrict immune responses. Translation of the fundamental mechanisms of TNF superfamily is leading to the design of therapeutics that can alter pathogenic processes in several autoimmune diseases or promote immunity to tumors.

Control of Metastasis by NK Cells

The metastatic spread of malignant cells to distant anatomical locations is a prominent cause of cancer-related death. Metastasis is governed by cancer-cell-intrinsic mechanisms that enable neoplastic cells to invade the local microenvironment, reach the circulation, and colonize distant sites, including the so-called epithelial-to-mesenchymal transition. Moreover, metastasis is regulated by microenvironmental and systemic processes, such as immunosurveillance. Here, we outline the cancer-cell-intrinsic and -extrinsic factors that regulate metastasis, discuss the key role of natural killer (NK) cells in the control of metastatic dissemination, and present potential therapeutic approaches to prevent or target metastatic disease by harnessing NK cells.

Ex vivo expanded natural killer cells from breast cancer patients and healthy donors are highly cytotoxic against breast cancer cell lines and patient-derived tumours

BACKGROUND

Natural killer (NK) cells play a critical role in cancer immunosurveillance. Recent developments in NK cell ex-vivo expansion makes it possible to generate millions of activated NK cells from a small volume of peripheral blood. We tested the functionality of ex vivo expanded NK cells in vitro against breast cancer cell lines and in vivo using a xenograft mouse model. The study aim was to assess functionality and phenotype of expanded NK cells from breast cancer patients against breast cancer cell lines and autologous primary tumours.

METHODS

We used a well-established NK cell co-culture system to expand NK cells ex vivo from healthy donors and breast cancer patients and examined their surface marker expression. Moreover, we tested the ability of expanded NK cells to lyse the triple negative breast cancer and HER2-positive breast cancer cell lines MDA-MB-231 and MDA-MB-453, respectively. We also tested their ability to prevent tumour growth in vivo using a xenograft mouse model. Finally, we tested the cytotoxicity of expanded NK cells against autologous and allogeneic primary breast cancer tumours in vitro.

RESULTS

After 3 weeks of culture we observed over 1000-fold expansion of NK cells isolated from either breast cancer patients or healthy donors. We also showed that the phenotype of expanded NK cells is comparable between those from healthy donors and cancer patients. Moreover, our results confirm the ability of ex vivo expanded NK cells to lyse tumour cell lines in vitro. While the cell lines examined had differential sensitivity to NK cell killing we found this was correlated with level of major histocompatibility complex (MHC) class I expression. In our in vivo model, NK cells prevented tumour establishment and growth in immunocompromised mice. Finally, we showed that NK cells expanded from the peripheral blood of breast cancer patients show high cytotoxicity against allogeneic and autologous patient-derived tumour cells in vitro.

CONCLUSION

NK cells from breast cancer patients can be expanded similarly to those from healthy donors, have a high cytotoxic ability against breast cancer cell lines and patient-derived tumour cells, and can be compatible with current cancer treatments to restore NK cell function in cancer patients.

Herpesvirus Entry Mediator and Ocular Herpesvirus Infection: More than Meets the Eye

As its name suggests, the host receptor herpesvirus entry mediator (HVEM) facilitates herpes simplex virus (HSV) entry through interactions with a viral envelope glycoprotein. HVEM also bridges several signaling networks, binding ligands from both tumor necrosis factor (TNF) and immunoglobulin (Ig) superfamilies with diverse, and often opposing, outcomes. While HVEM was first identified as a viral entry receptor for HSV, it is only recently that HVEM has emerged as an important host factor in immunopathogenesis of ocular HSV type 1 (HSV-1) infection. Surprisingly, HVEM exacerbates disease development in the eye independently of entry. HVEM signaling has been shown to play a variety of roles in modulating immune responses to HSV and other pathogens, and there is increasing evidence that these effects are responsible for HVEM-mediated pathogenesis in the eye. Here, we review the dual branches of HVEM function during HSV infection: entry and immunomodulation. HVEM is broadly expressed; intersects two important immunologic signaling networks; and impacts autoimmunity, infection, and inflammation. We hope that by understanding the complex range of effects mediated by this receptor, we can offer insights applicable to a wide variety of disease states.

Evidence for CD16a-Mediated NK Cell Stimulation in Antibody-Mediated Kidney Transplant Rejection

BACKGROUND

Natural killer (NK) cells localize in the microcirculation in antibody-mediated rejection (AMR) and have been postulated to be activated by donor-specific anti-HLA antibodies triggering their CD16a Fc receptors. However, direct evidence for NK cell CD16a triggering in AMR is lacking. We hypothesized that CD16a-inducible NK cell-selective transcripts would be expressed in human AMR biopsies and would offer evidence for CD16a triggering.

METHODS

We stimulated human NK cells through CD16a in vitro, characterized CD16a-inducible transcripts, and studied their expression in human kidney transplant biopsies with AMR and in an extended human cell panel to determine their selectivity.

RESULTS

In NK cells, CD16a stimulation induced increased expression of 276 transcripts (FC > 2x, false discovery rate < 0.05), including IFNG, TNF, CSF2, chemokines, such as CCL3, CCL4, and XCL1, and modulators of NK cell effector functions (TNFRSF9, CRTAM, CD160). Examination in an extended human cell panel revealed that CD160 and XCL1 were likely to be selective for NK cells in AMR. In biopsies, 8 of the top 30 CD16a-inducible transcripts were highly associated with AMR (P < 5 × 10): CCL4, CD160, CCL3, XCL1, CRTAM, FCRL3, STARD4, TNFRSF9. Other NK cell transcripts (eg, GNLY) were increased in AMR but not CD16a-inducible, their presence in AMR probably reflecting NK cell localization.

CONCLUSIONS

The association of CD16a-inducible NK cell-selective transcripts CD160 and XCL1 with biopsies with AMR provides evidence for NK cell CD16a activation in AMR. This raises the possibility of other CD16a-triggered effects that are not necessarily transcriptional, including NK localization and cytotoxicity.

Natural Killers Are Made Not Born: How to Exploit NK Cells in Lung Malignancies

In recent years, progress has been made in the characterization of natural killer (NK) cells in lung malignancies, and we have now gained a better understanding of the frequency, localization, phenotype, and functional status of NK cells infiltrating these tumors. NK cell subset recruited in lung cancer is mainly capable of producing relevant cytokines rather than exerting direct cancer cell killing. Thus, the relevance of NK cells in tumor microenvironment might also go beyond the killing of tumor cells, being NK cells endowed with regulatory functions toward an ample array of immune effectors. Nevertheless, boosting their cytotoxic functions and redirecting the migration of cytotoxic NK cell subset to the tumor site might open new therapeutic avenues for lung cancer. Also, we believe that a deeper investigation into the impact of both conventional (e.g., chemotherapy) or new therapies (e.g., anti-immune checkpoints mAbs) on NK cell homeostasis in lung cancer patients is now required.

Modulation of cytotoxic responses by targeting CD160 prolongs skin graft survival across major histocompatibility class I barrier

CD160 is a glycosylphosphatidylinositol-anchored protein of the immunoglobulin superfamily. It exhibits a pattern of expression coincident in humans and mice that is mainly restricted to cytotoxic cells and to all intestinal intraepithelial T lymphocytes. B- and T-lymphocyte attenuator (BTLA) and CD160 interact with cysteine-rich domain 1 of the extracellular region of Herpesvirus entry mediator (HVEM). CD160 engagement by HVEM can deliver inhibitory signals to a small subset of human CD4 T cells and attenuate its proliferation and cytokine secretion, but can also costimulate natural killer cells or intraepithelial lymphocytes. In turn, CD160 and BTLA can also function as agonist ligands being capable of costimulating T cells through membrane HVEM. Based on the restricted pattern of CD160 expression in cytotoxic cells, we postulated that CD160 may represent a suitable target for immune intervention in the setting of transplantation to modulate allogeneic cytotoxic responses. We demonstrated that in vivo administration of anti-CD160 antibody in combination with anti-CD40 L antibody to limit CD4 T-cell help modulated cytotoxic responses in a major histocompatibility complex class I mismatched model of allogeneic skin graft transplantation (bm1 donor to C57BL/6 recipient) and significantly prolonged graft survival. The implementation of this strategy in transplantation may reinforce current immunosuppression protocols and contribute to a better control of CD8 T-cell responses.

Regulation of Murine Natural Killer Cell Development

Natural killer (NK) cells are effector lymphocytes of the innate immune system that are known for their ability to kill transformed and virus-infected cells. NK cells originate from hematopoietic stem cells in the bone marrow, and studies on mouse models have revealed that NK cell development is a complex, yet tightly regulated process, which is dependent on both intrinsic and extrinsic factors. The development of NK cells can be broadly categorized into two phases: lineage commitment and maturation. Efforts to better define the developmental framework of NK cells have led to the identification of several murine NK progenitor populations and mature NK cell subsets, each defined by a varied set of cell surface markers. Nevertheless, the relationship between some of these NK cell subsets remains to be determined. The classical approach to studying both NK cell development and function is to identify the transcription factors involved and elucidate the mechanistic action of each transcription factor. In this regard, recent studies have provided further insight into the mechanisms by which transcription factors, such as ID2, FOXO1, Kruppel-like factor 2, and GATA-binding protein 3 regulate various aspects of NK cell biology. It is also becoming evident that the biology of NK cells is not only transcriptionally regulated but also determined by epigenetic alterations and posttranscriptional regulation of gene expression by microRNAs. This review summarizes recent progress made in NK development, focusing primarily on transcriptional regulators and their mechanistic actions.

A long noncoding RNA positively regulates CD56 in human natural killer cells

Natural killer (NK) cells are innate immune lymphocytes that play critical roles in host defense against viral infection and surveillance against malignant transformation. Long noncoding RNAs (lncRNAs) are important immune system regulators. Here, we analyzed human primary lymphocyte lncRNA expression profiles to identify NK-lncRNA signatures. We detected numerous novel NK-specific lncRNAs with potential roles in regulating human NK cell differentiation and function. Expression of lnc-CD56, an NK-specific lncRNA, was positively correlated with that of CD56, a classical human NK cell surface marker. We showed that lnc-CD56 may function as a positive regulator of CD56 in primary human NK cells and differentiated NK cells from human CD34+ hematopoietic progenitor cells. Our data provide an annotated human NK cell lncRNA expression catalog and demonstrate a key role for lncRNAs in NK cell biology.

T Cells Going Innate

Natural killer (NK) cell receptors (NKRs) play a crucial role in the homeostasis of antigen-experienced T cells. Indeed, prolonged antigen stimulation may induce changes in the receptor repertoire of T cells to a profile that features NKRs. Chronic antigen exposure, at the same time, has been shown to trigger the loss of costimulatory CD28 molecules with recently reported intensified antigen thresholds of antigen-experienced CD8(+) T cells. In transplantation, NKRs have been shown to assist allograft rejection in a CD28-independent fashion. We discuss here a role for CD28-negative T cells that have acquired the competency of the NKR machinery, potentially promoting allorecognition either through T cell receptor (TCR) crossreactivity or independently from TCR recognition. Collectively, NKRs can bring about innate-like T cells by providing alternative costimulatory pathways that gain relevance in chronic inflammation, potentially leading to resistance to CD28-targeting immunosuppressants.

Mouse models for studies of HLA-G functions in basic science and pre-clinical research

HLA-G was described originally as a tolerogenic molecule that allows the semiallogeneic fetus to escape from recognition by the maternal immune response. This review will discuss different steps in the study of HLA-G expression and functions in vivo, starting with analyses of expression of the HLA-G gene and its receptors in transgenic mice, and continuing with applications of HLA-G and its receptors in prevention of allograft rejection, transplantation tolerance, and controlling the development of infection. Humanized mouse models have been discussed for developing in vivo studies of HLA-G in physiological and pathological conditions. Collectively, animal models provide an opportunity to evaluate the importance of the interaction between HLA-G and its receptors in terms of its ability to regulate immune responses during maternal-fetal tolerance, survival of allografts, tumor-escape mechanisms, and development of infections when both HLA-G and its receptors are expressed. In addition, in vivo studies on HLA-G also offer novel approaches to achieve a reproducible transplantation tolerance and to develop personalized medicine to prevent allograft rejection.

The ETS1 transcription factor is required for the development and cytokine-induced expansion of ILC2

Zook et al. use a novel mouse model to demonstrate a requirement for the transcription factor ETS1 in the development and function of group 2 innate lymphoid cells.

Group 2 innate lymphoid cells (ILC2s) are a subset of ILCs that play a protective role in the response to helminth infection, but they also contribute to allergic lung inflammation. Here, we report that the deletion of the ETS1 transcription factor in lymphoid cells resulted in a loss of ILC2s in the bone marrow and lymph nodes and that ETS1 promotes the fitness of the common progenitor of all ILCs. ETS1-deficient ILC2 progenitors failed to up-regulate messenger RNA for the E protein transcription factor inhibitor ID2, a critical factor for ILCs, and these cells were unable to expand in cytokine-driven in vitro cultures. In vivo, ETS1 was required for the IL-33–induced accumulation of lung ILC2s and for the production of the T helper type 2 cytokines IL-5 and IL-13. IL-25 also failed to elicit an expansion of inflammatory ILC2s when these cells lacked ETS1. Our data reveal ETS1 as a critical regulator of ILC2 expansion and cytokine production and implicate ETS1 in the regulation of Id2 at the inception of ILC2 development.

Relationship between neurotoxic kynurenine metabolites and reductions in right medial prefrontal cortical thickness in major depressive disorder

Reductions in gray matter volume of the medial prefrontal cortex (mPFC), especially the rostral and subgenual anterior cingulate cortex (rACC, sgACC) are a widely reported finding in major depressive disorder (MDD). Inflammatory mediators, which are elevated in a subgroup of patients with MDD, activate the kynurenine metabolic pathway and increase production of neuroactive metabolites such as kynurenic acid (KynA), 3-hydroxykynurenine (3HK) and quinolinic acid (QA) which influence neuroplasticity. It is not known whether the alterations in brain structure and function observed in major depressive disorders are due to the direct effect of inflammatory mediators or the effects of neurotoxic kynurenine metabolites. Here, using partial posterior predictive distribution mediation analysis, we tested whether the serum concentrations of kynurenine pathway metabolites mediated reductions in cortical thickness in mPFC regions in MDD. Further, we tested whether any association between C-reactive protein (CRP) and cortical thickness would be mediated by kynurenine pathway metabolites. Seventy-three unmedicated subjects who met DSM-IV-TR criteria for MDD and 91 healthy controls (HC) completed MRI scanning using a pulse sequence optimized for tissue contrast resolution. Automated cortical parcellation was performed using the PALS-B12 Brodmann area atlas as implemented in FreeSurfer in order to compare the cortical thickness and cortical area of six PFC regions: Brodmann areas (BA) 9, 10, 11, 24, 25, and 32. Serum concentrations of kynurenine pathway metabolites were determined by high performance liquid chromatography (HPLC) with tandem mass spectrometry (MS/MS) detection, while high-sensitivity CRP concentration was measured immunoturbidimetrically. Compared with HCs, the MDD group showed a reduction in cortical thickness of the right BA24 (p<0.01) and BA32 (p<0.05) regions and MDD patients with a greater number of depressive episodes displayed thinner cortex in BA32 (p<0.05). Consistent with our previous findings in an overlapping sample, the KynA/3HK ratio and the log KynA/QA were reduced in the MDD group relative to the HC group (p's<0.05) and symptoms of anhedonia were negatively correlated with log KynA/QA in the MDD group (p<0.05). Both KynA/3HK and log KynA/QA at least partially mediated the relationship between diagnosis and cortical thickness of right BA32 (p's<0.05). CRP was inversely associated with BA32 thickness (p<0.01) and KynA/3HK partially mediated the relationship between CRP and the thickness of right BA32 (p<0.05). The results raise the possibility that the relative imbalance between KynA and neurotoxic kynurenine metabolites may partially explain the reductions in mPFC thickness observed in MDD, and further that these changes are more strongly linked to the putative effects of neuroactive kynurenine metabolites than those of inflammatory mediators.

Negative immune checkpoints on T lymphocytes and their relevance to cancer immunotherapy

The term 'inhibitory checkpoint' refers to the broad spectrum of co-receptors expressed by T cells that negatively regulate T cell activation thus playing a crucial role in maintaining peripheral self-tolerance. Co-inhibitory receptor ligands are highly expressed by a variety of malignancies allowing evasion of anti-tumour immunity. Recent studies demonstrate that manipulation of these co-inhibitory pathways can remove the immunological brakes that impede endogenous immune responses against tumours. Antibodies that block the interactions between co-inhibitory receptors and their ligands have delivered very promising clinical responses, as has been shown by recent successful trials targeting the CTLA-4 and PD-1 pathways. In this review, we discuss the mechanisms of action and expression pattern of co-inhibitory receptors on different T cells subsets, emphasising differences between CD4(+) and CD8(+) T cells. We also summarise recent clinical findings utilising immune checkpoint blockade.

Role of NK cells in immunotherapy and virotherapy of solid tumors

Although natural killer (NK) cells are endowed with powerful cytolytic activity against cancer cells, their role in different therapies against solid tumors has not yet been fully elucidated. Their interactions with various elements of the tumor microenvironment as well as their possible effects in contributing to and/or limiting oncolytic virotherapy render this potential immunotherapeutic tool still difficult to exploit at the bedside. Here, we will review the current literature with the aim of providing new hints to manage this powerful cell type in future innovative therapies, such as the use of NK cells in combination with new cytokines, specific mAbs (inducing ADCC), Tyr-Kinase inhibitors, immunomodulatory drugs and/or the design of oncolytic viruses aimed at optimizing the effect of NK cells in virotherapy.

Tricking the balance: NK cells in anti-cancer immunity

Natural Killer (NK) cells are classically considered innate immune effector cells involved in the first line of defense against infected and malignant cells. More recently, NK cells have emerged to acquire properties of adaptive immunity in response to certain viral infections such as expansion of specific NK cell subsets and long-lasting virus-specific responses to secondary challenges. NK cells distinguish healthy cells from abnormal cells by measuring the net input of activating and inhibitory signals perceived from target cells through NK cell surface receptors. Acquisition of activating ligands in combination with reduced expression of MHC class I molecules on virus-infected and cancer cells activates NK cell cytotoxicity and release of immunostimulatory cytokines like IFN-γ. In the cancer microenvironment however, NK cells become functionally impaired by inhibitory factors produced by immunosuppressive immune cells and cancer cells. Here we review recent progress on the role of NK cells in cancer immunity. We describe regulatory factors of the tumor microenvironment on NK cell function which determine cancer cell destruction or escape from immune recognition. Finally, recent strategies that focus on exploiting NK cell anti-cancer responses for immunotherapeutic approaches are outlined.

Innate Immune Defenses Mediated by Two ILC Subsets Are Critical for Protection against Acute Clostridium difficile Infection

Infection with the opportunistic enteric pathogen Clostridium difficile is an increasingly common clinical complication that follows antibiotic treatment-induced gut microbiota perturbation. Innate lymphoid cells (ILCs) are early responders to enteric pathogens; however, their role during C. difficile infection is undefined. To identify immune pathways that mediate recovery from C. difficile infection, we challenged C57BL/6, Rag1(-/-) (which lack T and B cells), and Rag2(-/-)Il2rg(-/-) (Ragγc(-/-)) mice (which additionally lack ILCs) with C. difficile. In contrast to Rag1(-/-) mice, ILC-deficient Ragγc(-/-) mice rapidly succumbed to infection. Rag1(-/-) but not Ragγc(-/-) mice upregulate expression of ILC1- or ILC3-associated proteins following C. difficile infection. Protection against infection was restored by transferring ILCs into Ragγc(-/-) mice. While ILC3s made a minor contribution to resistance, loss of IFN-γ or T-bet-expressing ILC1s in Rag1(-/-) mice increased susceptibility to C. difficile. These data demonstrate a critical role for ILC1s in defense against C. difficile.

Increased CD160 expression on circulating natural killer cells in atherogenesis

BACKGROUND

Atherosclerosis (AS) presents characteristic of a chronic inflammatory disease in which both adaptive and innate immune cells play roles. Accumulating evidence has showed the impairment of natural killer (NK) cells in atherosclerosis, however, the mechanisms of this impairment remain unclear. In this study, we investigated the expression of CD160 on NK cells and assessed its pathological roles in NK loss during atherogenesis.

METHODS

CD160 expression on NK cells was measured in 49 AS patients and 41 healthy controls (HC) by flow cytometry, their inflammatory cytokine levels in sera were determined by ELSIA, and the effect of CD160 engagement on NK cells was evaluated by in vitro culture experiments.

RESULTS

Compared to HC, AS patients had a significantly increased CD160 expression on peripheral NK cells and concomitantly decreased peripheral NK cell number, and increased CD160 expression was positively related to the levels of serum lipids and IFN-γ, TNF-α and IL-6 inflammation cytokines, which all are risk factors for atherogenesis, and inversely correlated with peripheral NK cell number. Furthermore, engagement of CD160 receptor on NK cells from AS patients triggers a significantly increased production of inflammation cytokines and subsequent NK cell apoptosis, and blockade of TNF-α prevented the increased apoptosis of NK cells from AS patients after CD160 engagement, indicating a critical role of TNF-α in mediating NK cell loss by CD160 engagement.

RESULTS

Our results provide evidence that elevated CD160 expression on NK cells plays an important role in NK cell loss in atherosclerosis. The increased CD160 expression on NK cells might be used as an indicator for disease progression.

Development, Homeostasis, and Heterogeneity of NK Cells and ILC1

Natural killer (NK) cells are a population of cytotoxic innate lymphocytes that evolved prior to their adaptive counterparts and constitute one of the first lines of defense against infected or mutated cells. NK cells are rapidly activated, expressing an array of germ-line encoded receptors that allow them to scan for protein irregularities on cells and kill those deemed "altered-self." NK cells rapidly produce a broad range of cytokines and chemokines following activation by virus, bacterial, or parasitic infection and are thus key in orchestrating inflammation. NK cells have previously been viewed to represent a relatively homogeneous group of IFN-γ-producing cells that express the surface markers NK1.1 and natural killer cell p46-related protein (NKp46 or NCR1 encoded by Ncr1) and depend on the transcription factor T-bet for their development. Recently, a second subset of T-bet-dependent innate cells, the group 1 innate lymphoid cells (ILC1), has been discovered which share many attributes of conventional NK (cNK) cells. Despite the similarities between ILC1 and cNK cells , they differ in several important aspects including their localization, transcriptional regulation, and phenotype suggesting each subset has distinct origins and functions in immune responses. Previously, the ability to detect and spontaneously kill cells that exhibit "altered-self" which is central to tumor and viral immunity has been thought to be an attribute restricted solely to cNK cells. The identification of ILC1 challenges this notion and suggests that key contributions from ILC1 may have gone unrecognized. Thus, understanding the different rules that govern the behavior of ILC1 and cNK cells in immune responses may potentially open unexpected doorways to uncover novel strategies to manipulate these cells in treating disease. Here, we review recent advances in our understanding of peripheral cNK cell and ILC1 heterogeneity in terms of their development, phenotype, homeostasis, and effector functions.