Tumour‐experienced T cells promote NK cell activity through trogocytosis of NKG2D and NKp46 ligands

Natural killer (NK) cells trigger cytotoxicity and interferon (IFN)‐γ secretion on engagement of the natural‐killer group (NKG)2D receptor or members of the natural cytotoxicity receptor (NCR) family, such as NKp46, by ligands expressed on tumour cells. However, it remains unknown whether T cells can regulate NK cell‐mediated anti‐tumour responses. Here, we investigated the early events occurring during T cell–tumour cell interactions, and their impact on NK cell functions. We observed that on co‐culture with some melanomas, activated CD4⁺ T cells promoted degranulation, and NKG2D‐ and NKp46‐dependent IFN‐γ secretion by NK cells, probably owing to the capture of NKG2D and NKp46 ligands from the tumour‐cell surface (trogocytosis). This effect was observed in CD4⁺, CD8⁺ and resting T cells, which showed substantial amounts of cell surface major histocompatibility complex class I chain‐related protein A on co‐culture with tumour cells. Our findings identify a new, so far, unrecognized mechanism by which effector T cells support NK cell function through the capture of specific tumour ligands with profound implications at the crossroad of innate and adaptive immunity.     

The two-faces of NK cells in oncolytic virotherapy

Oncolytic viruses (OVs) are immunotherapeutics capable of directly killing cancer cells and with potent immunostimulatory properties. OVs exert their antitumor effect, at least partially, by activating the antitumor immune response, of which NK cells are an important component. However, if on the one hand increasing evidence revealed that NK cells are important mediators of oncolytic virotherapy, on the other hand, NK cells have evolved to fight viral infections, and therefore they can have a detrimental effect for the efficacy of OVs. In this review, we will discuss the dichotomy between the antitumor and antiviral functions of NK cells related to oncolytic virotherapy. We will also review NK cell-based and OV-based therapies, engineered OVs aimed at enhancing immune stimulation, and combination therapies involving OVs and NK cells currently used in cancer immunotherapy.     

NK cells in allogeneic bone marrow transplantation

NK cells, until recently an ignored subset of lymphocytes, have begun to emerge as important cytotoxic effectors. It is now accepted that NK cells together with T cells constitute major actors in graft-versus-leukemia reaction after allogeneic bone marrow transplantation (BMT). Over the last several years the mechanisms regulating the activation of NK cells have been the subject of intense investigations encouraged by the clinical implications that these studies will have. This article provides a general overview of NK-cells biology and regulation pertinent to their function in allogeneic BMT, followed by a review of the in vivo preclinical and clinical evidence for the beneficial effect of NK cells in the adoptive immunotherapy of leukemia.     

Lipoprotein lipase protects bovine endothelial cells from human NK cytotoxic activity

Human lipoprotein lipase (LPL), in a dose dependent fashion, significantly inhibited spontaneous human natural killer (NK) cells, but not lymphokine-activated killer (LAK) cytotoxic activity against bovine pulmonary endothelial cells. The effect was dependent on endothelial heparan sulfate (HS) sites, since heparitinase reverted it. When HS is added before LPL, NK and LAK cytotoxicity are markedly reduced. Endothelial and NK cell priming, with LPL and HS+LPL, significantly induced CD40 and CD154 expression, respectively. Furthermore, CD40 expression was inversely proportional to lytic units (R2 = 0.9, P < 0.001). Treating endothelial cells simultaneously with indomethacin, CD154 fusion protein, and Wortmanin prevented the CD40 effect increasing xenograft rejection. LPL and HS+LPL protect bovine endothelial cells from NK cytotoxicity by inducing CD40, CD154 expression, and secretion of soluble factors. The high, non-modulated expression of adhesion receptors and the low number of HS sites account for the minor effect of CD40 in LAK cytotoxic responses against bovine endothelial cells.     

Alteration of inhibitory and activating NK cell receptor expression on NK cells in HIV-infected Chinese

Natural killer (NK) cell function, based on the expression of activating and inhibitory natural killer receptors (NKRs), may become abnormal during human immunodeficiency virus (HIV) infection. In this study, we investigated changes in receptor expression with individual and combinational analysis on NK cell subsets in HIV-infected Chinese. The results showed that natural killer group 2 member D (NKG2D) expression on total NK cells decreased significantly in HIV infection, while the expressions of natural killer group 2 member A (NKG2A) and killer cell immunoglobulin-like receptor, three domains, long cytoplasmic tail 1 (KIR3DL1) on total NK cells were not significantly different between any of the groups including HIV-positive treatment-naïve group, AIDS treatment-naïve group, HAART-treatment AIDS group and HIV-negative control group. Individual analysis of NKG2A⁺ and KIR3DL1⁺ cells revealed no significant differences in expression in any NK cell subsets between any of the groups, but the combinational analysis of NKG2D⁻NKG2A⁺, and NKG2D⁻KIR3DL1⁺ on the NK CD56^dim cell subset in the AIDS group were increased compared to the HIV-negative control group. On the contrary, NKG2D⁻NKG2A⁺ expression on the CD56^bright subset decreased in the AIDS group compared to the control group. Highly active antiretroviral therapy (HAART) treatment almost completely restored the levels of these receptor expressions. The results indicate that the distinct alteration of activating and inhibitory NKR expression on NK cells and its subsets occurred during HIV progression. Moreover, the imbalanced change of activating and inhibitory NKRs on NK cells and its subsets may explain the impaired NK cell immunity in HIV infected individuals.     

NK cells: An attractive candidate for cancer therapy

Natural killer (NK) cells have significant capability in tumor immune-surveillance. The ability of lyse transformed cells immediately in an antigen-independent manner make them an attractive candidate for cancer cell therapy. Despite employment of NK cells in cancer immunotherapy, clinical trials are faced with serious limitations such as trouble with the penetration of NK cells in tumor sites, limited in vivo persistence, and tumor microenvironment interference. Taken together, the NK-cell cancer therapy is still infant scenario that has a long way to be translated in clinic. Current article first reviews characteristic features of NK lymphocytes. Then, it discusses about important disruptive barriers and motivator in the developmental stages of NK cells like as tumor microenvironment. Finally, some revolutionary approaches are highlighted utilizing of NK cells in cancer therapy.     

NK细胞与HIV/SIV感染相关性的研究进展

NK细胞作为天然免疫系统的重要组成部分,其在HIV/SIV感染后的免疫机制及如何发挥抗病毒作用成为近几年艾滋病研究的热点之一。研究中发现,伴随HIV/SIV的感染,NK细胞亚群比例发生改变同时伴有功能缺陷,这种变化与HIV/SIV慢性感染阶段病毒复制水平有显著相关性。并且由于归巢受体表达的改变引起NK细胞在HIV/SIV感染者体内不同组织间的重新分布。NK细胞表面的受体KIR3DL1和KIR3DS也表现出对HIV感染的抵抗作用。这些发现为我们进一步研究NK细胞的抗HIV/SIV病毒感染的免疫机制提供了新的思路和方向。     

Expression of murine killer immunoglobulin-like receptor KIRL1 on CD1d-independent NK1.1<Superscript>+</Superscript> T cells

Three mouse killer immunoglobulin-like receptors (KIRs), namely, KIR3DL1, KIRL1, and KIRL2, have recently been identified in C56BL/6 (B6) mice. However, only two Kir genes are found in the B6 mouse genome sequence data base. To clarify this discrepancy, we cloned Kir cDNAs from multiple strains of mice. Sequencing of the cDNA clones showed that the Kir3dl1 gene is found in C3H/HeJ and CBA/J but not in B6 mice. Analysis of the single nucleotide polymorphism data base suggested that Kir3dl1 is the C3H/HeJ and CBA/J allele of Kirl1. We generated mAb to the recombinant KIRL1 protein to investigate its expression pattern. The anti-KIRL1 mAb bound to NK1.1⁺ T cells but only very weakly or at undetectable levels to other lymphocytes including natural killer (NK) cells and conventional T cells. Among NK1.1⁺ T cells, conventional NK T cells stained with CD1d tetramer did not significantly bind anti-KIRL1 mAb, whereas CD1d-tetramer-negative subset was KIRL1-positive. Furthermore, the expression of KIRL1 is readily detected on NK1.1⁺ T cells from β₂-microglobulin-deficient B6 mice. Thus, KIRL1 is predominantly expressed on CD1d-independent NK1.1⁺ T cells.     

NK sensitivity of neuroblastoma cells determined by a highly sensitive coupled luminescent method

The measurement of natural killer (NK) cells toxicity against tumor or virus-infected cells especially in cases with small blood samples requires highly sensitive methods. Here, a coupled luminescent method (CLM) based on glyceraldehyde-3-phosphate dehydrogenase release from injured target cells was used to evaluate the cytotoxicity of interleukin-2 activated NK cells against neuroblastoma cell lines. In contrast to most other methods, CLM does not require the pretreatment of target cells with labeling substances which could be toxic or radioactive. The effective killing of tumor cells was achieved by low effector/target ratios ranging from 0.5:1 to 4:1. CLM provides highly sensitive, safe, and fast procedure for measurement of NK cell activity with small blood samples such as those obtained from pediatric patients.     

CD83+CCR7+ NK cells induced by interleukin 18 by dendritic cells promote experimental autoimmune uveitis

Natural killer (NK) cells have been reported to play a pathological role in autoimmune uveitis. However, the mechanisms regarding NK cells in uveitis and factors that affect NK‐cell activation in this condition remain unclear. Here, we report that the number of CD3^‐NK1.1⁺CD83⁺CCR7⁺ cells is increased in the inflamed eyes within a mouse model of experimental autoimmune uveitis (EAU), and these cells express elevated levels of NKG2D, CD69 and IFN‐γ. Adoptively transferring CD83⁺CCR7⁺NK cells aggravates EAU symptoms and increases the number of CD4⁺IFN‐γ⁺T cells and dendritic cells (DCs) within the eye. These CD83⁺CCR7⁺NK cells then promote the maturation of DCs and IFN‐γ expression within T cells as demonstrated in vitro. Furthermore, IL‐18, as primarily secreted by DCs in the eyes, is detected to induce CD83⁺CCR7⁺NK cells. In EAU mice, anti‐IL‐18R antibody treatment also decreases retinal tissue damage, as well as the number of infiltrating CD83⁺CCR7⁺NK cells, T cells and DCs in the inflamed eyes and spleens of EAU mice. These results suggest that CD83⁺CCR7⁺NK cells, as induced by IL‐18 that primarily secreted by DCs, play a critical pathological role in EAU. Anti‐IL‐18R antibody might serve as a potential therapeutic agent for uveitis through its capacity to inhibit CD83⁺CCR7⁺NK cells infiltration.     

Differential recognition of MHC class I molecules of xeno-/allo-endothelial cells by human NK cells

Using human umbilical vein endothelial cells (HUVEC) and porcine aortic endothelial cells (PAEC) as target cells, human peripheral blood NK cells (PBNK) and NK92 cells as effector cells, the differential cytotoxicities of NK cells to allo- and xeno-endothelial cells were studied. The influence of MHC class I molecules on the cytotoxicity of human NK cells was assayed using acid treatment, and blockades of MHC class I antigens, CD94 and KIR (NKB1). The results indicated that the killing of PAEC by the two kinds of NK cells is higher than that of HUVEC. After acid- treatment, the cytotoxicity of the two kinds of NK cells to PAEC and HUVEC is significantly enhanced, but the magnitude of the enhancement is different. The enhancement of NK killing to acid treated HUVEC is much greater than that to PAEC. Blockade of CD94 mAb did not alter the NK cytotoxicity, while blockade of NKB1 mAb enhanced the cytotoxicity of PBNK to HUVEC and PAEC by 95% and 29% respectively. The results above suggested that the differential recognition of MHC I molecules of xeno-endothelial cells by human NK cells could be the major reason for higher NK cytotoxicity to PAEC. KIR might be the primary molecule that transduced inhibitory signals when endothelial cells were injured by NK cells.     

Imbalance of peripheral B lymphocytes and NK cells in rheumatoid arthritis

The study was focused on several cellular immune disorders correlated with the imbalance between peripheral blood B lymphocytes and NK cells in severe rheumatoid arthritis. By flow cytometry we calculated the proportions of T, T helper, T cytotoxic/suppressor, B lymphocytes and natural killer cells in peripheral blood. The mitogen-induced proliferation of peripheral lymphocytes was measured by tritium-labeld uridine incorporation. Experimental data highlight a connection between annomal values of the B to natural killer cells ratio and disorders of the peripheral mononuclear cells concentration. We also showed that the polyclonal proliferation capacity of peripheral lymphocytes in rheumatoid arthritis is solely related to the B to natural killer cells ratio or to the natural killer cells proportion. The study reveals a potential role of the imbalance between proportions of peripheral B lymphocytes and natural killer cells in the immune pathogenesis of rheumatoid arthritis, thus pointing out an interrelation between the adaptive and innate immune systems.     

Differential recognition of MHC class I molecules of xeno-/allo-endothelial cells by human NK cells

Using human umbilical vein endothelial cells (HUVEC) and porcine aortic endothelial cells (PAEC) as target cells, human peripheral blood NK cells (PBNK) and NK92 cells as effector cells, the differential cytotoxicities of NK cells to allo- and xeno-endothelial cells were studied. The influence of MHC class I molecules on the cytotoxicity of human NK cells was assayed using acid treatment, and blockades of MHC class I antigens, CD94 and KIR (NKB1). The results indicated that the killing of PAEC by the two kinds of NK cells is higher than that of HUVEC. After acid-treatment, the cytotoxicity of the two kinds of NK cells to PAEC and HUVEC is significantly enhanced, but the magnitude of the enhancement is different. The enhancement of NK killing to acid treated HUVEC is much greater than that to PAEC. Blockade of CD94 mAb did not alter the NK cytotoxicity, while blockade of NKB1 mAb enhanced the cytotoxicity of PBNK to HUVEC and PAEC by 95% and 29% respectively. The results above suggested that the different     

生物肽SP对NK细胞活化性受体NCRs表达的影响

研究SP对NK92-MI细胞杀伤活性以及活化性受体NCRs(NKp46、NKp44和NKp30分子)的表达的影响,揭示SP对NK细胞杀伤功能的调节作用及其内在作用机制.MTT法测定NK92-MI细胞对K562细胞的杀伤活性;Real-Time PCR检测NCRs的mRNA表达;流式细胞术检测NCRs的膜表达.在10-14～10-8 mol/L浓度范围的SP作用24h,对NK92-MI细胞的杀伤活性有明显增强作用;10-14～10-8 mol/L的SP,均可增加NK92-MI细胞活化性受体NKp44、NKp46及NKp30的mRNA表达;该浓度范围的SP均可增加NKp46的膜表达水平,仅较低浓度( 10-14moL/L)的SP对NKp44的膜表达水平有增加作用,各浓度的SP对NKp30的膜表达水平均无明显影响.SP可通过上调活化性受体NCRs的表达水平来调节NK细胞的活性.     

Resident peritoneal NK cells

In this study, we describe a new population of NK cells that reside in the normal, uninflamed peritoneal cavity. Phenotypically, they share some similarities with the small population of CD49b(-), CD27(+) immature splenic NK cells, as well as liver NK cells, but they differ in their expression of CD62L, TRAIL, and EOMES. Functionally, the peritoneal NK cells resemble the immature splenic NK cells in their production of IFN-γ, GM-CSF, and TNF-α and in the killing of YAC-1 target cells. We also found that the peritoneum induces different behavior in mature and immature splenic NK cells. When transferred i.v. into RAGγc knockout mice, both populations undergo homeostatic proliferation in the spleen, but only the immature splenic NK cells are able to reach the peritoneum. When transferred directly into the peritoneum, the mature NK cells survive but do not divide, whereas the immature NK cells proliferate profusely. These data suggest that the peritoneum is not only home to a new subset of tissue-resident NK cells, but that it differentially regulates the migration and homeostatic proliferation of immature versus mature NK cells.     

NK cells and apoptosis

Natural killer (NK) cells are a cell of the innate immune system that play an important role in the early response to viral infections and tumours. Natural killer cells are cytolytic, and secrete cytokines that influence the developing antigen-specific immune response. In the present article the NK cell surface molecules regulating effector function, the NK cell effector mechanisms involved in apoptosis, and the role of NK cell effector mechanisms in immune responses are reviewed.