Immune evasion and therapeutic opportunities based on natural killer cells

Natural killer(NK)cells can elicit an immune response against malignantly transformed cells without recognizing antigens,and they also exhibit cytotoxic effects and immune surveillance functions in tumor immunotherapy.Although several studies have shown the promising antitumor effects of NK cells in immunotherapy,their function is often limited in the tumor microenvironment because tumor cells can easily escape NK cell-induced death.Thus,for efficient tumor immunotherapy,the mechanism by which tumor cells escape NK cell-induced cytotoxicity must be fully understood.Various novel molecules and checkpoint receptors that mediate the disruption of NK cells in the tumor microenvironment have been discovered.In this review,we analyze and detail the major activating and inhibitory receptors on the surface of NK cells to delineate the mechanism by which tumor cells suppress NKG2D ligand expression and increase tumor receptor and inhibitory receptor expression[NKG2A,programmed cell death1(PD-1),and T-cell immunoglobulin and immunoreceptor tyrosine inhibitory motif(TIGIT)]on the NK cell surface,and thus inhibit NK cell activity.We also reviewed the current status of treatments based on these surface molecules.By comparing the therapeutic effects related to the treatment status and bypass mechanisms,we attempt to identify optimal single or combined treatments to suggest new treatment strategies for tumor immunotherapy.

Investigation of the Cytotoxicity of CAR-NK-92 Cells Targeting CEA Against Gastric Cancer Cells

Objective:To construct CAR-NK-92 cells targeting carcinoembryonic antigen(CEA)and study their killing effect on gastric cancer cells.Methods:CAR-NK-92 cells targeting CEA were constructed.After co-culturing CAR-NK-92 cells with MKN-45 gastric cancer cells,the killing effect of CAR-NK-92 cells was detected by a lactate dehydrogenase release assay.The secretion levels of gamma interferon and granulocyte-macrophage colony-stimulating factor were measured using an ELISA assay.Results:The lactate dehydrogenase release assay showed that CAR-NK-92 cells had a significant killing effect on MKN-45 cells compared to CON-NK-92 cells,and the difference was statistically significant(P<0.001).ELISA results indicated that the levels of gamma interferon and granulocyte-macrophage colony-stimulating factor secreted by CAR-NK-92 cells and MKN-45 target cells were significantly increased after co-culture(P<0.001).Conclusion:CAR-NK-92 cells targeting CEA exhibit a significant killing effect on CEA-positive gastric cancer cells.

Targeted Therapy of CEA-CAR-NK Cells Against Colorectal Cancer Cells

Objective:Investigate the cytotoxic effect of CAR-NK cells targeting CEA on colorectal cancer cells with positive CEA expression.Methods:The mRNA and protein levels of CEA in different CRC cell lines were detected by qRT-PCR and Western blot analysis.Lentiviral transduction was used to construct CAR-NK cells and empty vector CON-NK cells targeting CEA.Fluorescence microscopy and WB were used to determine whether the cells successfully constructed and expressed CAR structures.The effector NK cells were co-cultured with target cells,and the levels of LDH,IFN-γ,and GM-CSF were detected.The killing rate of effector cells was calculated,and the release of cytokines during the killing of target cells by different effector cells was compared.Results:The expression level of CEA in colorectal cancer patients was significantly higher than that in normal samples and other tumor samples,and the prognosis survival time of patients with high CEA expression was lower than that of CRC patients with low or no CEA expression(P<0.05).The CEA expression of the HT29 cell line was significantly higher than that of the SW1116 cell line at both the mRNA and protein levels.CEA-CAR-NK92 cells and CON-NK92 cells expressed green fluorescence under a microscope,and WB results showed that CEA-CAR-NK92 cells successfully expressed the CAR structure.Compared with CON-NK92 cells and NK92 cells,CEA-CAR-NK92 cells effectively killed HT29 cells(P<0.05).CEA-CAR-NK92 cells secreted a large amount of IFN-γand GM-CSF during the killing of HT29 cells,while the cytokine secretion of CON-NK92 cells and NK92 cells was not significant(P<0.05).Conclusion:CAR-NK92 cells targeting CEA can effectively kill CEA-positive colorectal cancer cells.

Designing a risk prognosis model based on natural killer cell-linked genes to accurately evaluate the prognosis of gastric cancer

Background:This study was aimed at identifying natural killer(NK)cell-related genes to design a risk prognosis model for the accurate evaluation of gastric cancer(GC)prognosis.Methods:We obtained NK cell-related genes from various databases,followed by Cox regression analysis and molecular typing to identify prognostic genes.Various immune algorithms and enrichment analyses were used to investigate the mutations,immune status,and pathway variations among different genotypes.The key prognostic genes were assessed using the least absolute shrinkage and selection operator(Lasso)regression analysis and univariate Cox regression analysis.Thereafter,the risk score(RS)prognosis model was constructed based on the selected important prognostic genes.A Receiver Operating Characteristics(ROC)curve was plotted for analyzing the robustness of the model.Subsequently,the decision and calibration curves were used for assessing the reliability and prediction accuracy of the proposed model.The‘pRRophetic’R software package was utilized for predicting the half-maximal inhibitory concentration(IC50)of immunotherapy and chemotherapy drugs.Results:We screened 21 prognostic genes and three molecular subtypes and found that the C1 subtype had the worst prognosis.Further,the pathways promoting tumor proliferation,such as epithelial-mesenchymal transition were significantly up-regulated.The results also showed that the macrophages in the M2 stage were significantly infiltrated in the C1 subtype,and there was significant overexpression in the C1 subtype,accompanied by a severe inflammatory reaction.The C1 was highly sensitive to drugs like 5-fluorouracil and paclitaxel.The ROC,calibration curve,and decision curve showed that the risk model was robust and strongly reliable.Conclusion:Overall,our proposed NK cell-related RS model can be used as a more accurate prediction index for GC patients,providing a valuable contribution to personalized medicine.

Establishment of a prognostic model related to tregs and natural killer cells infiltration in bladder cancer

BACKGROUND Regulatory T cells(Tregs)and natural killer(NK)cells play an essential role in the development of bladder urothelial carcinoma(BUC).AIM To construct a prognosis-related model to judge the prognosis of patients with bladder cancer,meanwhile,predict the sensitivity of patients to chemotherapy and immunotherapy.METHODS Bladder cancer information data was obtained from The Cancer Genome Atlas and GSE32894.The CIBERSORT was used to calculate the immune score of each sample.Weighted gene co-expression network analysis was used to find genes that will have the same or similar expression patterns.Subsequently,multivariate cox regression and lasso regression was used to further screen prognosis-related genes.The prrophetic package was used to predict phenotype from gene expression data,drug sensitivity of external cell line and predict clinical data.RESULTS The stage and risk scores are independent prognostic factors in patients with BUC.Mutations in FGFR3 lead to an increase in Tregs percolation and affect the prognosis of the tumor,and additionally,EMP1,TCHH and CNTNAP3B in the model are mainly positively correlated with the expression of immune checkpoints,while CMTM8,SORT1 and IQSEC1 are negatively correlated with immune checkpoints and the high-risk group had higher sensitivity to chemotherapy drugs.CONCLUSION Prognosis-related models of bladder tumor patients,based on Treg and NK cell percolation in tumor tissue.In addition to judging the prognosis of patients with bladder cancer,it can also predict the sensitivity of patients to chemotherapy and immunotherapy.At the same time,patients were divided into high and low risk groups based on this model,and differences in genetic mutations were found between the high and low risk groups.

HBsAg stimulates NKG2D receptor expression on natural killer cellsand inhibits hepatitis C virus replication

Background： Higher hepatitis B surface antigen （HBsAg） facilitates hepatitis C virus （HCV） clearance inpatients with hepatitis B virus （HBV）/HCV co-infection. We investigated the effect of exogenous HBsAgon the inhibition of HCV replication mediated by natural killer （NK） cells.

The effects of stereotactic body radiotherapy on peripheral natural killer and CD3~+CD56~+ NKT-like cells in patients with hepatocellular carcinoma

Background: Both natural killer(NK) and CD3+CD56+ natural killer T(NKT)-like cells play critical roles in the antitumor response. This study aimed to explore the effects of stereotactic body radiotherapy(SBRT) on peripheral NK and NKT-like cells in patients with hepatocellular carcinoma(HCC), and to identify possible surface markers on these cells that correlate with the prognosis. Methods: Twenty-five HCC patients were prospectively enrolled in our study, and 10 healthy individuals were served as healthy controls. Flow cytometry was used to determine the counts and the percentages of peripheral NK and NKT-like cells, cells with certain receptors, and cells with intracellular interferon-γand TNF-α secretion at different time points, including time points of prior to SBRT, at post-SBRT, and 3-month and 6-month after treatment. The Kaplan-Meier method with the log-rank test was applied for survival analysis. Results: The peripheral NKT-like cells was increased at post-SBRT. Meanwhile, elevated levels of inhibitory receptors and reduced levels of activating receptors of NK cells were also observed in NK cells at post-SBRT, but the levels was not significantly different at 3-month and 6-month as compared with the baseline levels. Lower percentage of NKp30+ NK cells before SBRT and higher percentage of CD158b + NK cells after SBRT were associated with poor progression-free survival. In addition, higher percentage of CD3+CD56+ NKT-like cells was associated with a higher overall survival rate in HCC patients. Conclusions: SBRT has an apparent effect on both peripheral NK and CD3+ CD56+ NKT-like cells. Lower percentage of NKp30 + NK cells before SBRT and higher percentage of CD158b + NK cells after SBRT are correlated with poor patients' PFS. Higher percentage of CD3+ CD56+ NKT-like cells is associated with higher OS in HCC patients.

Human CD4- CD8- Invariant Natural Killer T Cells Promote IgG Secretion from B Cells Stimulated by Cross-Linking of Their Antigen Receptors

Immunoglobulin (Ig) M production can be induced by the interaction of thymus-independent type-2 (TI-2) antigen (Ag) with B cell Ag receptors (BCRs) without the involvement of conventional T cells;for IgG production through the same process, however, a second signal is required. Previous studies have reported that invariant natural killer T (iNKT) cells may be responsible for the second signal involved in IgG production. In the present study, we addressed whether human iNKT cells could participate in the production of Ig against TI-2 Ag in vitro. Two major distinct subsets of human iNKT cells, CD4+ CD8β- (CD4) and CD4- CD8β- [double negative (DN)] cells, were generated from peripheral blood monocytes from a healthy volunteer. BCR engagement, triggered by anti-IgM antibody stimulation, examined here as a model of BCR engagement triggered by TI-2 Ag, induced abundant IgM production by B cells. Both CD4 and DN iNKT cells reduced IgM production and conversely enhanced IgG production in a dose-dependent manner. In addition, IgG production by CD19+CD27- (naïve) and CD19+CD27+ (memory) B cells was predominantly promoted by DNiNKT cells rather than CD4 iNKT cells;nevertheless, IgM production by both B cell subsets was similarly reduced by either subset of iNKT cells. These results suggest that the DN iNKT subsets may preferentially promote Ig class switching by B cells upon stimulation with TI-2 Ag.

非小细胞肺癌患者血清CA211水平和NK细胞数与预后相关

目的 探究非小细胞肺癌(NSCLC)患者血清糖类抗原211(CA211)表达水平和自然杀伤(NK)细胞数与预后的相关性。方法 选取杭州师范大学附属医院2019年6月至2022年7月收治的132例NSCLC患者作为实验组,另选取同期收治的132例肺部良性病变患者作为对照组。从检验科收集数据分析NSCLC患者血清CA211表达水平和NK细胞数与患者预后关系以及影响NSCLC患者预后的相关因素。结果 实验组中性粒细胞/淋巴细胞值(NLR值)和血清CA211表达水平高于对照组(P<0.05),NK细胞数低于对照组(P<0.05);实验组血清CA211表达水平和NK细胞数呈负相关(r=-0.405,P<0.001);不同血清CA211表达水平和NK细胞数的患者淋巴结转移情况以及TNM分期存在显著性差异(P<0.05);CA211低表达者1年生存率高于CA211高表达者(P<0.05),NK细胞高水平者1年生存率高于NK细胞低水平者(P<0.05);淋巴结转移、TNM分期、CA211是影响NSCLC患者预后的危险因素(P<0.05),NK细胞是NSCLC患者预后的保护因素(P<0.05)。结论 NSCLC患者血清CA211表达水平及NK细胞数与临床病理特征及预后有密切联系。

治疗前淋巴细胞与C反应蛋白比值对结外NK/T细胞淋巴瘤预后的判断价值

目的:探讨治疗前淋巴细胞与C反应蛋白比值(LCR)对结外NK/T细胞淋巴瘤(ENKTL)预后的判断价值。方法:回顾性分析郑州大学第一附属医院收治的203例初诊为ENKTL患者的临床资料,ROC曲线得到LCR预测5 a总生存期(OS)的最佳截断值,并根据截断值将患者分为两组,绘制Kaplan-Meier生存曲线,采用Cox回归分析无进展生存期(PFS)和OS的影响因素。结果:LCR预测5 a OS的最佳截断值为0.19,低LCR组患者预后较差(P<0.001)。Cox回归分析结果表明,低LCR组ENKTL患者预后较差,PFS和OS的HR(95%CI)分别为0.462(0.336~0.636)和0.381(0.275~0.527)。结论:治疗前LCR可影响ENKTL预后,低LCR患者的预后较差。

具NK细胞的溶瘤病毒疗法的模型分析

本文建立了一类包含自然杀伤细胞(NK细胞)免疫反应的肿瘤病毒相互作用模型。首先分析了系统的边界性态,将系统的平衡点进行完整的分类,讨论了边界平衡点的局部稳定性,并从数值上验证了周期解的存在性,最后讨论了NK细胞在病毒治疗中所起到的作用。数值结果表明:a)整体肿瘤大小与病毒感染率成反比,与肿瘤生长速率成正比;b)对于NK细胞相关参数,NK细胞从淋巴结的流入速率越大,最终肿瘤越小;若产生NK细胞增殖,当增殖速率比较小时,相较于无NK增殖时,最终肿瘤变大,即较小的NK细胞增殖对治疗产生负面的影响,但当NK细胞的增殖速率过高时,将会导致肿瘤和病毒的完全清除。

Tumor immunotherapy: New aspects of natural killer cells

A group of impressive immunotherapies for cancer treatment, including immune checkpoint-blocking antibodies,gene therapy and immune cell adoptive cellular immunotherapy, have been established, providing new weapons to fight cancer. Natural killer（NK） cells are a component of the first line of defense against tumors and virus infections. Studies have shown dysfunctional NK cells in patients with cancer. Thus, restoring NK cell antitumor functionality could be a promising therapeutic strategy. NK cells that are activated and expanded ex vivo can supplement malfunctional NK cells in tumor patients. Therapeutic antibodies, chimeric antigen receptor（CAR）, or bispecific proteins can all retarget NK cells precisely to tumor cells. Therapeutic antibody blockade of the immune checkpoints of NK cells has been suggested to overcome the immunosuppressive signals delivered to NK cells.Oncolytic virotherapy provokes antitumor activity of NK cells by triggering antiviral immune responses. Herein,we review the current immunotherapeutic approaches employed to restore NK cell antitumor functionality for the treatment of cancer.

Distribution of natural killer cells and T-lymphocyte subsets in peripheral blood,gallbladder cancer and surrounding tissue

BACKGROUND: The patient with malignant tumor always show immunologic function drawback and ingravescent with tumor development, especially in the aspect of cell-mediated immunity. This study was undertaken to define the relationship between the immune function of local cells and cancer development by investigating the distribution of natural killer (NK) cells and T-lymphocyte subsets in peripheral blood, the cancer tissue and the tissue surrounding gallbladder carcinoma. METHODS: The numbers of CD4(+) and CD8(+) T-lymphocytes and NK cells were measured by flow cytometry in samples taken from gallbladder cancer tissue, the surrounding tissues and peripheral blood of 38 patients, and compared with the numbers in the peripheral blood and gallbladder tissue of 30 patients with cholecystitis as controls. RESULTS: The numbers of CD4(+) and CD8(+) T-cells and NK cells in gallbladder cancer tissues were significantly higher than those in the surrounding tissue and gallbladder with gallstone. However, the ratio of CD4(+)/CD8(+) was lower in the cancer tissue than that in the surrounding tissue and tissue from gallbladders with gallstones. The distribution of CD4(+) and CD8(+) T-cells and NK cells in mucous membrane of cholecystitis gallbladder and that in the tissue surrounding gallbladder cancer were significantly different. CONCLUSIONS: Disproportionate and imbalanced distribution of NK cells and subsets of T-lymphocytes occurs in the mucous membrane proper of gallbladder cancer and surrounding tissue. Although gallbladder cancer tissue has higher expressions of CD4(+), CD8(+) and NK cells, the immune function is low or in an inhibited state. In gallbladder cancer immunization therapy, local cellular immunological function should be enhanced and the protective barrier improved.

Human natural killer cells for targeting delivery of gold nanostars and bimodal imaging directed photothermal/photodynamic therapy and immunotherapy

Objective:To construct a novel nanoplatform GNS@CaCO3/Ce6-NK by loading the CaCO3-coated gold nanostars(GNSs)with Chlorin e6 molecules(Ce6)into human peripheral blood mononuclear cells(PBMCs)-derived NK cells for tumor targeted therapy.Methods:GNS@CaCO3/Ce6 nanoparticles were prepared and characterized by TEM and UV-vis.The cell surface markers and cytokines secretion of NK cells before and after loading the GNS@CaCO3/Ce6 nanoparticles were detected by Flow Cytometry(FCM)and ELISA.Effects of the GNS@CaCO3/Ce6-NK cells on A549 cancer cells was determined by FCM and CCK-8.Intracellular fluorescent signals of GNS@CaCO3/Ce6-NK cells were detected via Confocal laser scanning microscopic(CLSM)and FCM at different time points.Intracellular ROS generation of GNS@CaCO3/Ce6-NK cells under laser irradiation were examined by FCM.The distribution of GNS@CaCO3/Ce6-NK in A549 tumor-bearing mice were observed by fluorescence imaging and PA imaging.The combination therapy of GNS@CaCO3/Ce6-NK under laser irradiation were investigated on tumor-bearing mice.Results:The coated CaC03 shell on the surface of GNSs exhibited prominent delivery and protection effect of Ce6 during the cellular uptake process.The as-prepared multifunctional GNS@CaCO3/Ce6-NK cells possessed bimodal functions of fluorescence imaging and photoacoustic imaging.The as-prepared multifunctional GNS@CaCO3/Ce6-NK cells could actively target tumor tissues with the enhanced photothermal/photodynamic therapy and immunotherapy.Conclusions:The GNS@CaCO3/Ce6-NK shows effective tumor-targeting ability and prominent therapeutic efficacy toward lung cancer A549 tumor-bearing mice.Through fully utilizing the features of GNSs and NK cells,this new nanoplatform provides a new synergistic strategy for enhanced photothermal/photodynamic therapy and immunotherapy in the field of anticancer development in the near future.

Natural killer cells in hepatitis C:Current progress

Patients infected with the hepatitis C virus(HCV) are characterized by a high incidence of chronic infection, which results in chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. The functional impairment of HCV-specific T cells is associated with the evolution of an acute infection to chronic hepatitis. While T cells are the important effector cells in adaptive immunity, natural killer(NK) cells are the critical effector cells in innate immunity to virus infections. The findings of recent studies on NK cells in hepatitis C suggest that NK cell responses are indeed important in each phase of HCV infection. In the early phase, NK cells are involved in protective immunity to HCV. The immune evasion strategies used by HCV may target NK cells and might contribute to the progression to chronic hepatitis C. NK cells may control HCV replication and modulate hepatic fibrosis in the chronic phase. Further investigations are, however, needed, because a considerable number of studies observed functional impairment of NK cells in chronic HCV infection. Interestingly, the enhanced NK cell responses during interferon-α-based therapy of chronic hepatitis C indicate successful treatment. In spite of the advances in research on NK cells in hepatitis C, establishment of more physiological HCV infection model systems is needed to settle unsolved controversies over the role and functional status of NK cells in HCV infection.

Functional distinction of rat liver natural killer cells from spleen natural killer cells under normal and acidic conditions in vitro

BACKGROUND: The microenvironment within solid tumors has often been shown to exhibit an acidic extracellular pH. Although the morphologic and functional differences in natural killer (NK) cells of the liver and spleen have been reported previously under physiological conditions, the difference under acidic conditions is still unclear. This study was to investigate the differences in the morphological and functional characteristics between rat liver and spleen NK cells under normal and acidic conditions in vitro. METHODS: Liver and spleen NK cells were isolated and purified from Sprague-Dawley rats by density gradient centrifugation and the Dynabeads FlowComp TM Flexi system, and stimulated for 4 days with or without IL-2 or treated with low pH or control for different times. Morphology was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), cell death and proliferation assays were performed by flow cytometry, IFN-γ production was tested by ELISA, and cytotoxic activity was evaluated by lactate dehydrogenase (LDH) release assay. RESULTS: Liver NK cells had significantly higher levels of cytotoxic activity than spleen NK cells under normal and acidic conditions, and the maximum difference was observed at pH 5.6. Further analysis revealed that the cytotoxic activity of NK cells was correlated with morphology, cell death, proliferative activity and IFN-γ production. By TEM, liver NK cells contained a greater number of electron-dense granules per cell at pH 5.6.Moreover, a modest elevation of cell death and reduction of proliferation of liver NK cells occurred within a range of 5.6-7.2. Interestingly, an acidic extracellular pH only marginally, and not significantly, suppressed IFN-γ production by liver NK cells. CONCLUSION: The sharp morphological and functional differences shown by the two types of NK cells in vitro indicate that liver NK cells are unexpectedly resistant to pH shock.

细粒棘球蚴感染早期对小鼠肝脏NKT细胞及其相关因子的影响

目的探讨细粒棘球蚴感染早期对小鼠肝脏自然杀伤T(Natural killer T,NKT)细胞及其相关因子的影响。方法将24只雌性C57BL/6小鼠随机分为对照组与感染组,每组12只。感染组经肝门静脉接种细粒棘球蚴原头蚴,对照组注射等量生理盐水,4周后,每组各取6只小鼠的肝脏组织进行Masson染色,另外6只小鼠的肝脏组织用于分离淋巴细胞以进行流式细胞术检测小鼠肝脏不同NKT细胞亚群比例和相关细胞因子干扰素-γ(Interforn-γ,IFN-γ)、肿瘤坏死因子-α(Tumour necrosis factor-α,TNF-α)、白细胞介素-4(Interleukin-4,IL-4)、白细胞介素-10(Interleukin-10,IL-10)和白细胞介素-17A(Interleukin-17A,IL-17A)的表达。结果与对照组纤维占比比较,感染组肝脏侵袭部位及其邻近肝脏组织呈现结缔组织病变,纤维化明显,纤维占比显著增加,且分布较广,包绕肉芽肿四周形成条索状纤维间隔。与对照组比较,感染组小鼠肝脏NKT细胞比例和CD4^(+)NKT细胞比例显著降低,差异均有统计学意义(P均<0.01);与对照组比较,感染组小鼠肝脏NKT细胞分泌TNF-α的比例、CD4^(+)NKT细胞分泌TNF-α的比例显著升高,差异均有统计学意义(P<0.05)。结论细粒棘球蚴感染早期小鼠肝脏纤维化程度增加,肝脏NKT细胞及其亚群CD4^(+)NKT细胞产生TNF-α的水平增加,提示肝脏NKT细胞可能参与细粒棘球蚴感染早期肝脏免疫应答反应。

Association of the frequency of peripheral natural killer T cells with nonalcoholic fatty liver disease

AIM: To investigate whether changes in the frequencyof peripheral natural killer T (NKT) cells were correlatedwith liver disease in patients who had metabolicpredispositions to nonalcoholic fatty liver disease(NAFLD).METHODS: Peripheral blood samples were obtainedfrom 60 Chinese NAFLD patients and 60 age and gendermatched healthy controls. The frequency of peripheralNKT cells was detected by flow cytometry. Clinical andlaboratory data were collected for further analysis. RESULTS: NAFLD patients had a lower frequencyof peripheral NKT cells than healthy controls (1.21%± 0.06% vs 1.62% ± 0.07%, P < 0.001). Furtheranalysis revealed that the frequency of peripheralNKT cells was negatively correlated with body massindex, waist circumference and serum levels of alanineaminotransferase. Logistic regression analysis revealedthat elevated body mass index [hazard ratio (HR):2.991], aspartate aminotransferase levels (HR: 1.148)and fasting blood sugar (HR: 3.133) increased the riskof NAFLD, whereas an elevated frequency of peripheralNKT cells (HR: 0.107) decreased the risk. CONCLUSION: Changes in the frequency of peripheralNKT cells were correlated with NAFLD and a decreasedfrequency of peripheral NKT cells was a risk factor forNAFLD.

Research on stress-induced apoptosis of natural killer cells and the alteration of their killing activity in mouse liver

AIM:To investigate the stress-induced apoptosis of natural killer(NK)cells and the changes in their killing activity in mouse livers.METHODS:A restraint stress model was established in mice.Flow cytometry was employed to measure the percentage of NK cells and the changes in their absolute number in mouse liver.The cytotoxicity of hepatic and splenic NK cells was assessed against YAC-1 target cells via a 4 h 51Cr-release assay.RESULTS:The restraint stress stimulation induced the apoptosis of NK cells in the liver and the spleen,which decreased the cell number.The number and percentage of NK cells in the spleen decreased.However,the number of NK cells in the liver decreased,whereas the percentage of NK cells was significantly increased.The apoptosis of NK cells increased gradually with prolonged stress time,and the macrophage-1(Mac-1)+NK cells were more susceptible to apoptosis than Mac-1-NK cells.Large numbers of Mac-1-NK cells in the liver,which are more resistant to stress-induced apoptosis,were observed than the Mac-1-NK cells in the spleen.The stress stimulation diminished the killing activity of NK cells in the spleen was significantly decreased,but the retention of numerous Mac-1-NK cells in the liver maintained the killing ability.CONCLUSION:Significant stress-induced apoptosis was observed among Mac-1+NK cells,but not Mac-1-NK cells in the mouse liver.Stress stimulation markedly decreased the killing activity of NK cells in the spleen but remained unchanged in the liver.

自然杀伤(NK)细胞与2019冠状病毒病(COVID-19)发生发展的研究进展

自然杀伤(NK)细胞在清除病毒,执行免疫调节方面发挥着重要的作用,它通过分泌趋化因子以及与其他天然免疫细胞协同作用,被赋予天然免疫调节功能和获得性免疫反应。随着对严重急性呼吸综合征冠状病毒2(SARS-CoV-2)感染的2019冠状病毒病(COVID-19)的研究深入,发现NK细胞在其中发挥着重要作用。SARS-CoV-2感染会影响NK细胞的分布和效应功能,NK细胞的免疫应答或可影响新冠肺炎患者的预后。本文总结了近年来NK细胞在COVID-19感染中作用的研究现状,并且讨论了以NK细胞作为治疗剂的可能性,以期为防治SARS-CoV-2的免疫损害提供潜在思路。