Regulation Of NK Cell Function Research Articles

Transcriptional Regulation of the Natural Cytotoxicity Receptor NKp44 Gene in Human NK Cell Leukemia

The natural cytotoxicity receptor NKp44 is an important regulator of NK cell function. We have previously reported that NKp44 has binding affinity to heparin and the transferrin containing multimeric sialyl Lewis X produced by human hepatoma HepG2 cells (HepTF) is more highly expressed than the other natural cytotoxicity receptors. To further understand the differences between natural cytotoxicity receptors, we sought to understand the gene transcriptional regulation of NKp44 in KHYG-1 human NK leukemia cells. 5′-rapid amplification of cDNA ends revealed the location of the NKp44 transcription initiation sites allowing identification of the 5′ untranscribed region. The result of the dual luciferase assay suggested that regulation of NKp44 gene expression is affected by the -1963 to -1599 nt region and the -352 to -231 nt region relative to the transcription initiation sites. The -410 to +1 nt region contained potential binding sites for the transcription factors AP-1, Oct-1, HNF-4, and Pax-4. These results suggest that defined regions in the 5′-flanking region of NKp44 gene is important for NKp44 transcription and regulation.

Overexpression of LLT1 (CLEC2D) in childhood Acute Lymphoblastic Leukemia (ALL)

Abstract Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer in the developed world with peak incidence between the ages of 2 and 5 years. Despite current treatment protocols achieving significant improvement in survival of ALL patients, serious acute and late complications are frequent and resistance to chemotherapy often develops. Although NK cells have long been known to mediate antigen independent tumor killing, the therapeutic potential of NK cell-based immunotherapy has yet to be realized. NK cells have the capacity to kill virus-infected or tumor-transformed cells and they express several surface molecules that regulate NK cell function both positively and negatively. We have previously identified 2B4 (CD244), CS1 (CRACC) and LLT1 (CLEC2D) to play a major role in NK cell activation. In this study, we evaluated the cell surface and mRNA expression of NK cell receptors in 42 ALL subjects and 20 healthy subjects both male and female in the age range of 2 – 20 yrs from different racial/ethnic groups. The peripheral blood samples were collected and analyzed by flow cytometry and real-time PCR for expression. A significant increase in the expression of LLT1 in the T and NK cell populations was observed in ALL subjects as compared to healthy subjects. NK cells from 3 ALL subjects also showed impaired cytotoxic function as they demonstrated lower killing of K562 cells compared to a healthy subject. These results indicate that LLT1 may play a role in NK-mediated surveillance of childhood ALL.

MiRNAs in NK Cell-Based Immune Responses and Cancer Immunotherapy.

The incidence of certain forms of tumors has increased progressively in recent years and is expected to continue growing as life expectancy continues to increase. Tumor-infiltrating NK cells may contribute to develop an anti-tumor response. Optimized combinations of different cancer therapies, including NK cell-based approaches for targeting tumor cells, have the potential to open new avenues in cancer immunotherapy. Functional inhibitory receptors on NK cells are needed to prevent their attack on healthy cells. Nevertheless, disruption of inhibitory receptors function on NK cells increases the cytotoxic capacity of NK cells against cancer cells. MicroRNAs (miRNAs) are small non-coding RNA molecules that target mRNA and thus regulate the expression of genes involved in the development, maturation, and effector functions of NK cells. Therapeutic strategies that target the regulatory effects of miRNAs have the potential to improve the efficiency of cancer immunotherapy. Interestingly, emerging evidence points out that some miRNAs can, directly and indirectly, control the surface expression of immune checkpoints on NK cells or that of their ligands on tumor cells. This suggests a possible use of miRNAs in the context of anti-tumor therapy. This review provides the current overview of the connections between miRNAs and regulation of NK cell functions and discusses the potential of these miRNAs as innovative biomarkers/targets for cancer immunotherapy.

Regulation of NK-Cell Function by HLA Class II

Natural Killer (NK) cells were initially described as part of the innate immune system and characterized by their ability to lyse malignant and virus-infected cells. The cytolytic function of NK cells is tightly controlled by activating and inhibitory receptors expressed on the cell surface. Ligands that interact with a variety of NK-cell receptors include the human leukocyte antigen (HLA) molecules, and the regulation of NK-cell function by HLA class I molecules is well-established. Earlier studies also suggested a role of HLA class II molecules in regulating NK cell activity; yet, interactions between HLA class II molecules and NK cell receptors have not been well-characterized. We recently identified a subset of HLA-DP molecules that can serve as ligands for the natural cytotoxicity receptor NKp44 and activate NK cells. This novel receptor-ligand interaction provides a potential mechanism to explain the strong associations of HLA-DP molecules with HBV infection outcomes, graft-vs.-host disease and inflammatory bowel disease. Furthermore, it adds a new mechanism for NK-cell crosstalk with immune cells expressing HLA class II molecules. In this perspective article, we discuss the potential implications of NK cell receptor interactions with HLA class II molecules for the regulation of immune responses.

Abstract WP319: miRNA Screening of Natural Killer Cell Identifies miR-1224 as a Post-Transcriptional Regulator of NK Cell Function After Ischemic Stroke

Objectives: To screen miRNA profile of peripheral NK cells in ischemic stroke mouse model and investigate a most promising candidate (miR-1224) for post-transcriptional regulation of NK cell function after ischemic stroke. Methods: Mice were subjected to a 60 min focal cerebral ischemia produced by transient intraluminal occlusion of MCAO. For NK cell isolation, cell suspensions from the spleens after reperfusion were enriched for NK cells using magnetic-bead sorting system after staining with anti-NK1.1 microbeads. The nCounter Mouse miRNA array was used to analyze miRNA expression profile in splenic NK cells over the time course of experimental ischemic stroke. Based on the miRNA data, we further in vitro modulated miR-1224 in NK cells using mimics or inhibitor, then injected i.v into Rag2-/-γc-/- recipient mice. Neurological function score was compared and spontaneous infection was assessed by pulmonary bacteria colony culture, and changes in potential signaling pathway (SP1/TNF-α) were verified by rt-PCR and western blot. Results: Through miRNA expression profile analysis, we have identified significant changes at each time point in peripheral NK cells after cerebral ischemia. Among all screened miRNA, miR-1224 remarkably increased in MCAO group, which was verified by PCR. Then isolated NK cells treated with mimics or inhibitors, were transferred to Rag2-/-γc-/- recipient mice. Compared with WT mice, Rag2-/-γc-/- mice with miR-1224 inhibitor exhibited increased NK cell number, enhanced NK cell activation/cytotoxicity feature, as well as better neurological behaviors and reduced pulmonary infection after MCAO. Moreover, compared with the control group, NK cells with miR-1224 inhibitor showed significantly increased SP1 gene and protein phosphorylation. As SP1 gene is one of the potential targets of miR-1224, this study suggests that miR-1224 may regulate NK cell function after MCAO, which is associated with SP1 pathway. Conclusion: The miRNA profiling of splenic NK cells provided insight into the functional mechanism and signaling pathways underlying the distinct organ-specific NK cell properties, which will contribute to the better understanding of NK cell mediated immune-response in relation to different stages of stroke.

Deletion of CISH in Human Pluripotent Stem Cell-Derived Natural Killer Cells Enhances Anti-Tumor Activity Via Metabolic Reprogramming

Cellular metabolism is now recognized to play a key role in regulating function and differentiation of immune cells. Immune cells undergo dynamic metabolic shifts to support their activity. Recent studies have shown the importance of metabolism to regulate NK cell function under different conditions. IL-15 can regulate NK cell metabolism in a dose- and time- dependent manner. However, whether improving metabolic fitness of NK cells can lead to improved anti-tumor activity is largely unknown. Here, we deleted CIS (encoded by the CISH gene in human induced pluripotent stem cells (iPSC)-derived NK cells (CISH-/- iPSC-NK) using CRISPR/Cas9 technology. CIS is known to function as a critical negative regulator of IL-15 signaling and a potent inhibitory checkpoint in NK cell-mediated anti-tumor activity. Surprisingly, more than 3000 differentially expressed genes were identified in CISH-/- iPSC-NK cells through RNA sequencing analysis. Gene ontology (GO) enrichment analysis showed that the top 2 up-regulated signaling pathways were associated with leukocyte differentiation and activation. Notably, more than 50 genes that involved in positive regulation of lymphocyte activation including genes associated with NK cell effector functions were significantly up-regulated in CISH-/- iPSC-NK cells compared with unmodified iPSC-NK cells. As expected, CISH-/- iPSC-NK cells exhibited increased sensitivity to IL-15 stimulation. Specifically, IL-15 stimulated JAK1 tyrosine phosphorylation, STAT3 and STAT5 phosphorylation were all dramatically increased in CISH-/- iPSC-NK cells, compared with unmodified iPSC-NK cells. In addition, when incubated with low concentrations of IL-15 (5 ng/ml), a concentration that does not support the growth and functions of unmodified iPSC-NK cells, CISH-/- iPSC-NK cells maintained significantly better expansion with >10 fold expansion for CISH-/- iPSC-NK cells in 3 weeks, whereas most of WT iPSC-NK cells died under these conditions (p<0.001). These CISH-/- iPSC-NK cells exhibited improved cytotoxic against acute myeloid leukemia (AML) cell lines K562 and Molm-13. More importantly, in an AML (MOLM-13) xenograft model, CISH-/- iPSC-NK cells displayed significantly increased in vivo persistence thus lead to significantly better control of tumor progression. To further understand the underling mechanisms contributing to the increased functionality in CISH-/- iPSC-NK cells, we then analyzed the metabolic profiles of these cells using Agilent Seahorse assays. After treatment with low concentration IL-15 for 7 days, CISH-/- iPSC-NK cells displayed both increased glucose metabolism and increased mitochondrial respiration profiles when compared with unmodified iPSC-NK cells. Increased glucose metabolism include a significant increase in basal glycolysis (p=0.0003, 84.5 ± 1.0 vs 61.1 ± 1.8 mpH/min, n=6), and glycolytic capacity (p=0.0049, 15.2±0.4 vs 11.7±0.5 mpH/min, n=6). And increased mitochondrial respiration profile is characterized by an increase in the spare respiratory capacity (p=0.0009, 16.3±1.9 vs 6.9±0.5 pmol/min, n=6), maximal respiration (p<0.0001, 31.6±1.9 vs 15.7±0.8 pmol/min, n=6) and ATP-linked respiration (p<0.0001, 11.5 ± 0.4 vs 7.0±0.3 pmol/min, n=6). Interestingly, limiting the increase of glucose metabolism and mitochondrial respiration via utilization of an mTOR inhibitor (rapamycin) attenuated the increased functionality in CISH-/- iPSC-NK cells. The findings presented here show that deletion of CISH in iPSC-NK cells enhance anti-tumor activity, at least in part via metabolic reprogramming. These findings suggest that improving NK cell functions for cancer immunotherapy through metabolic reprogramming provides a promising therapeutic strategy. Disclosures Guan: OncoImmune: Equity Ownership. Kaufman:FATE Therapeutics: Consultancy, Research Funding.

IDO1 impairs NK cell cytotoxicity by decreasing NKG2D/NKG2DLs via promoting miR-18a

BackgroundIndoleamine-2,3-dioxygenase 1 (IDO1) is an important enzyme for altering the tumour microenvironment and assisting tumour cells to escape the immune system. ResultsIn this study, a significant reduction in NK cell cytotoxicity that was associated with a high expression of IDO1 in a reconstructed tumour microenvironment was observed. In a co-culture system of tumour cell culture supernatant (TSN) and murine NK cell, IDO1 was substantially increased, while NKG2D was markedly downregulated in NK cells. Based on computational predictions, miR-18a, which has two definite binding sites consisting of the 3′UTR of NKG2D and the 3′UTR of NKG2D ligand (Mult-1), was suspected to be a negative regulator of which its conjoined. As expected, the IDO1 could promote the expression of miR-18a and promote the downregulation effect of miR-18a on NKG2D and NKG2DL, and INCB024360 (INCB) could reverse the result. For digging the mechanism deeper, we authenticated IDO1 promoted the combination of miR-18a and AGO2 after argonaute 2 (AGO2) co-immunoprecipitation, which then degraded Mult-1 mRNA and inhibited the translation of it, further destructing NK cell cytotoxicity. ConclusionOur findings revealed a new regulatory axis, IDO1/miR-18a/NKG2D/NKG2DL, in the regulation of NK cell function. This may provide insight into the mechanism of the priming effect of IDO1 inhibitors and miR-18a interference, then elicit possible new methods of cancer treatment.

The yin-yang of the interaction between myelomonocytic cells and NK cells.

NK cells are innate lymphoid cells, which play a key role in the immune response to cancer and pathogens and participate in the shaping of adaptive immunity. NK cells engage in a complex bidirectional interaction with myelomonocytic cells. In particular, macrophages, dendritic cells and neutrophils promote differentiation and effector function of NK cells and, on the other hand, myelomonocytic cells express triggers of checkpoint blockade (eg PD-L1) and other immunosuppressive molecules, which negatively regulate NK cell function. In addition, NK cells express high levels of IL-1R8, which acts as a checkpoint for IL-18 driven differentiation and activation of NK cells. Evidence suggests that targeting the myeloid cell-NK cell crosstalk unleashes effective anti-tumour and anti-viral resistance.

Semaphorin-3E Produced by Immature Dendritic Cells Regulates Activated Natural Killer Cells Migration.

Natural killer (NK) cells and dendritic cells (DCs) are two innate immune cells that are critical in regulating innate and adaptive immunity. Cellular functions and migratory responses of NK or DC can be further regulated in NK-DC crosstalk that involves multiple cytokine signals and/or direct cell-cell contacts. Semaphorin-3E (Sema-3E) is a member of a large family of Semaphorin proteins that play diverse regulatory functions in different biological systems upon its binding to the cognate receptors. However, possible role(s) of Sema-3E on the regulation of NK-cell functions has not been elucidated. Here, we first demonstrated that DC and NK cells expressed Sema-3E and its receptors, respectively. To formally address the importance of DC-derived Sema-3E in regulating NK-cell migration, we compared in vitro migratory responses of activated NK cells (aNKs) toward different conditioned media of DCs (immature, lipopolysaccharide- or Poly I:C-stimulated) derived from Sema-3E+/+ or Sema-3E−/− mice. We observed that aNKs exhibited enhanced migrations toward the conditioned medium of the immature Sema-3E−/− DC, when compared with that of the immature Sema-3E+/+ DC. Addition of exogenous recombinant Sema-3E to the conditioned medium of the Sema-3E−/− immature DC (iDC) abrogated such enhanced NK-cell migration. Our current work revealed a novel role of Sema-3E in limiting NK-cell migrations toward iDC in NK-DC crosstalk.

Kbtbd2 inhibits the cytotoxic activity of immortalized NK cells through down-regulating mTOR signaling in a mouse hepatocellular carcinoma model.

Natural killer cell (NK cell)-based immunotherapy is a promising therapeutic strategy for hepatocellular carcinoma (HCC). However, the molecular mechanisms underlying the regulation of NK cell function in the tumor sites are not completely elucidated. In this study, we identified the enhanced expression of kelch repeat and BTB (POZ) domain containing 2(Kbtbd2) in intratumoral NK cells in a mouse HCC implantation model as a negative regulator of NK cells. To investigate this interaction, we used a Tet-on inducibleexpression system to control Kbtbd2 expression in an immortalized mouse NK cell line KIL C.2. With this approach, we found that overexpression of Kbtbd2 reduced KIL C.2 cell proliferation, decreased expression certain of Ly49 receptor family members, and substantially impaired cytotoxic activity of KIL C.2 cells in vitro. Moreover, phosphorylation of mTOR and its target 4E-binding protein 1 was reduced in Kbtbd2-expressing KIL C.2 cells, along with down-regulated phosphorylation of Erk1/2. Adoptively transferred Kbtbd2-expressing KIL C.2 cells exhibited weaker tumoricidal effect on hepatocellular carcinoma cells in the HCC implantation model, in comparison with transferred control KIL C.2 cells. Taken together, our investigation indicates that Kbtbd2 is an inhibitory molecule for the tumoricidal activity of KIL C.2 cells and perhaps intratumoral NK cells.

Blockade of CD112R and TIGIT signaling sensitizes human natural killer cell functions.

Trastuzumab is the first-line drug to treat breast cancer with high Her2 expression. However, many cancers failed to respond, largely due to their resistance to NK cell-triggered antibody-dependent cellular cytotoxicity (ADCC). Poliovirus receptor (PVR)-like molecules are known to be important for lymphocyte functions. We found that all PVR-like receptors are expressed on human NK cells, and only TIGIT is preferentially expressed on the CD16+ NK cell subset. Disrupting the interactions of PVR-like receptors with their ligands on cancer cells regulates NK cell activity. More importantly, TIGIT is upregulated upon NK cell activation via ADCC. Blockade of TIGIT or CD112R, separately or together, enhances trastuzumab-triggered antitumor response by human NK cells. Thus, our findings suggest that PVR-like receptors regulate NK cell functions and can be targeted for improving trastuzumab therapy for breast cancer.

MicroRNA in hormonal mechanisms of regulation of NK cell function

We investigated the effect of human chorionic gonadotropin, estriol, leptin, ghrelin, and kisspeptin on the microRNA expression in separated NK cells. All of these hormones are able to effectively modulate the expression of microRNAs both stimulating and suppressing the cytotoxic potential of NK cells and thereby indirectly regulate the functions of these lymphocytes.

Involvement of NFAT Transcription Factors in NK Cell Reactivity

NK cells are lymphoid components of innate immunity and play an important role in tumor immunosurveillance. One of the major transcriptional regulators in lymphoid cells is NFAT (Nuclear Factor of Activated T Cells), as highlighted by its important role in T and B cell development and function. With regard to NK cells, available data indicate that NFAT is dispensable for development. However, several lines of evidence including the observation that the immunosuppressive drugs cyclosporin A and tacrolimus, which mediate their effects through inhibition of calcineurin and consecutively NFAT, influence NK reactivity implicate a role of this family of transcription factors in NK cell reactivity and function. Here we employed different genetic mouse models on the C57BL/6 background to directly study the functional role of NFAT in NK cells.We found that except for NFAT3 mRNA and protein of all family members (NFAT 1, 2, 4 and 5) was expressed in resting NK cells of wild type (WT) mice with NFAT1, 2 and 4 being most abundantly detectable. When we employed NK cells with knockout (KO) of NFAT 1, 2, and 4 in comparative in vitro analyses, we surprisingly found that lack of NFAT resulted in enhanced NK cell activation, degranulation and release of immunomodulatory cytokines like IFN-γ after co-culture with YAC-1 target cells as well as increased production of granzyme B and perforin after cytokine activation. The inhibitory effect of NFAT on NK cell effector function was further confirmed in vivo by employing WT and germ line NFAT KO animals in the syngeneic B16 melanoma model, which revealed a significantly reduced metastatic burden in NFAT KO mice. Depletion of NK cells in this model system in turn resulted in increased metastasis, however, with WT animals displaying significantly higher metastatic burden compared to NFAT KO mice. As this pointed to the fact that NFAT influences metastasis via both NK-dependent and independent mechanisms, we further generated mice with a NK cell-specific (conditional Ncr1-Cre dependent) NFAT2 KO. When these animals were employed again in analyses of B16 lung metastasis, comparative analyses with WT animals confirmed the inhibitory effect of NFAT on NK tumor immunosurveillance.Taken together, these results provide the first direct evidence for the functional involvement of NFAT in NK cell antitumor reactivity and, in contrast to T and B cells, identify NFAT as a negative regulator of NK cell function. DisclosuresNo relevant conflicts of interest to declare.

Killer Cell Lectin-like Receptor G1 Inhibits NK Cell Function through Activation of Adenosine 5'-Monophosphate-Activated Protein Kinase.

NK cells are the first line of defense against infected and transformed cells. Defective NK cell activity was shown to increase susceptibility for viral infections and reduce tumor immune-surveillance. With age, the incidence of infectious diseases and malignancy rises dramatically, suggesting that impaired NK cell function might contribute to disease in these individuals. We found an increased frequency of NK cells with high expression of the inhibitory killer cell lectin-like receptor G1 (KLRG1) in individuals >70 y. The role of KLRG1 in ageing is not known, and the mechanism of KLRG1-induced inhibition of NK cell function is not fully understood. We report that NK cells with high KLRG1 expression spontaneously activate the metabolic sensor AMP-activated protein kinase (AMPK) and that activation of AMPK negatively regulates NK cell function. Pre-existing AMPK activity is further amplified by ligation of KLRG1 in these cells, which leads to internalization of the receptor and allows interaction with AMPK. We show that KLRG1 activates AMPK by preventing its inhibitory dephosphorylation by protein phosphatase-2C rather than inducing de novo kinase activation. Finally, inhibition of KLRG1 or AMPK prevented KLRG1-induced activation of AMPK and reductions in NK cell cytotoxicity, cytokine secretion, proliferation, and telomerase expression. This novel signaling pathway links metabolic sensing, effector function, and cell differentiation with inhibitory receptor signaling that may be exploited to enhance NK cell activity during ageing.

T-bet and Eomesodermin in NK Cell Development, Maturation, and Function.

Recent reports give insights into the role of the T-box transcription factors, T-bet and Eomesodermin (Eomes), in NK cell biology. In this mini-review, we recapitulate the initial reports that delineate T-bet and Eomes as master regulators of NK cell development, maturation, and function. We discuss how T-bet and Eomes expression is regulated during NK cell development and peripheral maturation. Furthermore, we summarize the current literature on the role of T-bet and Eomes in the transcriptional regulation of NK cell function and review possible effects of T-box transcription factor anomalies during aging, infection, cancer, and after hematopoietic stem cell transplantation. We discuss how the current data argue in favor of a model of T-bet and Eomes synergy in transcriptional regulation of NK cell function and identify T-box transcription factors as potential targets for therapeutic interventions.

Pulmonary NK cells prevent allergic airway sensitization: Regulation by CB2 cannabinoid receptors

Abstract Allergic asthma is a chronic inflammatory disease involving the interaction between the innate and adaptive immune response. Endogenously generated cannabinoids, acting via CB receptors play important roles in both homeostatic and inflammatory processes. CB2-active compounds are known to impact innate immunity including responses by monocytes and NK cells. However, the contribution of pulmonary NK cells and CB2-active endocannabinoids to the innate events preceding sensitization of the airways to the common house dust mite (HDM) allergen is unclear. We investigated the significance of CB2 activation during allergen-triggered pulmonary inflammation and NK cell effector function. Allergic airway inflammation was induced in mice by sensitization via the airways by intranasal HDM instillation, and responses in wild type (WT) and CB2-deficient (CB2−/−) mice were compared. Mice lacking CB2 receptor exhibited elevated numbers of pulmonary NK cells yet were resistant to the induction of allergic inflammation and showed diminished airway hyperreactivity, pulmonary eosinophilia, TH2 cytokine production and mucus secretion after allergen inhalation. Cellular depletion and adoptive transfer studies were undertaken to dissect the mechanisms involved. Depletion of NK cells restored HDM responsiveness. Conversely, transfer of CB2−/− NK cells into WT mice suppressed the allergic airway inflammation and was associated with a reduction in monocyte-derived dendritic cells but elevated CX3CL1 release and recruitment of Ly6C−CX3CR1+ monocytes. These studies established a crucial role for CB2 activation in allergic lung disease via regulation of NK cell function and identified novel therapeutic targets for treatment of asthma.

The Diverse Role of NK Cells in Immunity to Toxoplasma gondii Infection.

The obligate intracellular parasite Toxoplasma gondii (T. gondii), found in ~30% of humans worldwide, is a significant health risk for people with HIV/AIDS, people undergoing chemotherapy treatment or organ transplantation, and for developing fetuses as a result of congenital infection [1]. Infection can cause death, blindness, spontaneous abortion, or mental retardation and is correlated with behavior and neurocognitive changes [2]. No therapies exist to prevent or clear parasite infection, which is lifelong. CD8 T cell interferon (IFN)γ is the major mechanism of protection [3,4]; however, many immune factors contribute to successful parasite control. One is the natural killer cell (NK cell) [5]. NK cells are considered group 1 innate lymphoid cells (ILCs) and provide defense against tumors and intracellular pathogens (viruses, bacteria, and parasites) [6]. They use surface receptors (activating, inhibitory, and cytokine) to survey host cells and tissues for damage or infection. Receptor engagement stimulates killing of diseased target cells (cytotoxicity) and initiating IFNγ production. Activating receptors recognize specific ligands expressed on target cell surfaces and activate via cytoplasmic immunoreceptor tyrosine-based activation motifs (ITAM) or associated adapter molecules DAP10 and DAP12 [7]. Inhibitory receptors inhibit by assessing self through MHC Class I (MHCI) recognition and, when triggered, recruit ITAM-antagonizing phosphatases SHIP1 and SHP1 via cytoplasmic immunoreceptor tyrosine-based inhibitory motifs (ITIM) [8]. Inflammatory cytokines IFNα/β, Interleukin (IL)-2, IL-12, IL-15, and IL-18 synergize with activating receptor signals or stimulate NK cell activation alone [7]. Other functional surface proteins include FcγRs, Fas, and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Ultimately, these surface proteins regulate NK cell function depending upon the stimulatory environment. Studies of NK cell responses to T. gondii have broadly impacted parasite immunology and NK cell fields. Thus, T. gondii is an excellent and relevant model to investigate NK cell biology. This model will be important in future studies, given newly emerging NK cell adaptive immune and regulatory roles and their therapeutic potential.

Contradicting roles of miR-182 in both NK cells and their host target hepatocytes in HCV

Background and aimNatural killer cells are part of the innate immunity involved in viral eradication and were shown to be greatly affected by HCV infection. Epigenetic regulation of NK cell function by microRNAs was not efficiently studied before and was never studied in HCV infection; therefore the aim of this study was to assess for the first time the role of microRNAs in regulating the function of NK cells of HCV-infected patients and hence viral replication in the target HCV-infected Huh7 cells. MethodologyNK cells were isolated from PBMCs of HCV-infected patients as well as controls, and HCV-infected liver biopsies as well as Huh7 cells infected with the virus were used. For the infection of Huh7 cells, first viral vector was in-vitro transcribed into viral RNA that was then used to infect naїve Huh7 cells. Supernatant from the infected cells was then collected and used for further infection. For manipulation of NK cells or Huh7 cells, miR-182 mimics and inhibitors were transfected via lipofection method. RNA was extracted from each cell population, reverse transcribed. Gene expression as well as viral load was quantified using qPCR. ResultsScreening of NKG2A and NKG2D between patients and controls showed no difference in expression of NKG2A, while NKG2D was found to be downregulated. In view of that, bioinformatics analysis was performed and showed that miR-182 has potential binding sites on both the inhibitory receptor NKG2A and the activating receptor NKG2D, and on its ligand ULBP2, as well as on the viral genome itself. In NK cells of HCV-infected patients, miR-182 was found to be over-expressed compared to controls; its ectopic expression was found to decrease NKG2D mRNA level, while miR-182 inhibitors were able to decrease NKG2A mRNA compared to untransfected cells. In addition, co-culturing genotype 4 or 2 HCV-infected Huh7 cells with miR-182 mimicked NK cells of HCV-infected patients showed decreased viral replication, suggesting an enhanced NK cell function. On the other hand, miR-182 and ULBP2 were both found to be downregulated in HCV liver tissues and HCV-infected Huh7 cells compared to their controls. miR-182 mimics were found to decrease ULBP2 mRNA and increase viral replication in genotypes 4 and 2 HCV-infected target (Huh7) cells compared to controls, while miR-182 inhibitor decreased viral replication in the cell models. ConclusionmiR-182 was never investigated before, neither in HCV infection nor in NK cells, and we found it to have dysregulated expression in both liver tissues and NK cells of HCV-infected patients compared to control. In addition to that, miR-182 was found to have a contradicting effect in both effector cell and its HCV-infected target cell regarding HCV replication.

Basic understanding of the HLA system in allogeneic hematopoietic cell transplantation

Human immune responses are principally characterized by the human leukocyte antigen (HLA) system, a diverse set of cell surface molecules encoded by the major histocompatibility complex gene cluster on the short arm of chromosome 6. Among various members of the HLA family, the best characterized are the classic highly polymorphic class I and class II molecules that are responsible for antigen presentation to T cells and regulation of NK cell functions. In allogeneic hematopoietic cell transplantation, sophisticated approaches to donor-recipient allele-level matching at 3 class I (HLA-A/B/C) and 3 class II (HLA-DRB1/DQB1/DPB1) loci have been proven to lower the risk of immunologic complications such as graft failure and graft-versus-host disease, and possibly to confer effective graft-versus-malignancy effects. Future areas of research include clarifying the role of relatively non-polymorphic non-classical HLA molecules (HLA-E/F/G, HLA-DM/DO) and polymorphic/non-polymorphic class I-related molecules (MICA, MICB, HFE, MR1, CD1, FcRn) in the immune regulation that follows hematopoietic cell transplantation.

Complexes of DNA with the Antimicrobial Peptide LL37 Augment NK Cell Functions by Inducing Type I Interferon Production from Circulating Monocytes and Plasmacytoid Predendritic Cells.

The cationic antimicrobial peptide, LL37, forms electrostatic complexes with DNA (LL37-DNA), which are potent activators of circulating plasmacytoid predendritic cells (ppDCs) and monocytes. However, the effects of LL37-DNA on other immune cell types, such as NK cells, are poorly characterized. In this study, we show that complexes of human genomic DNA (hgDNA) or synthetic double-stranded oligodeoxynucleotides with LL37 strongly enhance natural cytotoxicity of human peripheral blood mononuclear cells (PBMCs) upon an overnight culture, whereas hgDNA alone has no effect, and LL37 alone is moderately active. LL37-DNA complexes potentiate degranulation of, and interferon (IFN)-γ production by, NK cells upon subsequent encounter of K562 target cells. The complexes do not influence percentages of NK cells among PBMCs or the expression of cytotoxic proteins by NK cells. Using neutralizing anticytokine antibodies and immunomagnetic depletion of different subpopulations of PBMCs, we found that the effect of LL37-DNA on NK cells is indirect and mediated by type I IFNs produced by monocytes and, to a lesser extent, by ppDCs. We discuss possible roles of LL37-DNA complexes in the regulation of NK cell functions and in the treatment of cancer.