Suppression of natural killer cell activity on Candida stellatoidea by a 50 Hz magnetic field

Exposure to electromagnetic fields (EMF) is ubiquitous for almost all individuals living in industrialized countries. Epidemiological and laboratory studies suggest that exposure to Extremely Low Frequency (ELF) EMF increase cancer risk. The immune system functions as one of the body's main protective mechanisms, and Natural Killer (NK) cells are a subset of lymphocytes that can destroy several types of tumor cells. In this study, we investigated, NK cell activity after exposure to a 50 Hertz (Hz), 2 mT magnetic field generated by a Helmholtz Coil. Nineteen male, 10-12 week old guinea pigs were used, and NK cytotoxic activity of splenocytes was measured in vitro by natural anticandidial colorimetric index. The Mann-Whitney U test was applied for statistical analysis. NK cell cytotoxic activity was decreased in exposed compared to controls. Our data suggests that part of the immune system, the NK cell, can be suppressed by a 50 Hz magnetic field.     

Enhancement of Natural Killer cell cytotoxicity by a CD18 integrin-activating antibody

Natural Killer (NK) cells kill certain tumor cells and virus infected cells in an antigen-independent manner. Members of CD18 integrins such as CD11a, CD11b, and CD11c are expressed in all NK cells. CD18-blocking mAbs inhibit the killing activity of NK cells implying an essential role of these integrins in NK cell cytotoxicity. In this report we show that the pan CD18-activating mAb, 240Q, augments cytotoxicity of resting NK cells. Since activation of either CD11a or CD11c alone fails to augment the NK cell activity, we postulate that a functional synergy of the individual CD18 integrins is responsible for the observed stimulatory effect of pan CD18 activation on NK cell cytotoxicity.     

Virulizin, a novel immunotherapy agent, activates NK cells through induction of IL-12 expression in macrophages

Virulizin, a novel biological response modifier, has demonstrated significant antitumor efficacy in a variety of human tumor xenograft models including melanoma, pancreatic cancer, breast cancer, ovarian cancer and prostate cancer. The significant role of macrophages and NK (Natural killer) cells was implicated in the antitumor mechanism of Virulizin where expansion as well as increased activity of macrophages and NK cells were observed in mice treated with Virulizin. Depletion of macrophages compromised Virulizin-induced NK1.1⁺ cell infiltration into xenografted tumors and was accompanied by reduced antitumor efficacy. In the present study, involvement of macrophages in NK cell activation was investigated further. We found that depletion of NK cells in CD-1 nude mice by anti-ASGM1 antibody significantly compromised the antitumor activity of Virulizin. Cytotoxicity of NK cells isolated from Virulizin-treated mice was enhanced against NK-sensitive YAC-1 cells and C8161 human melanoma cells, but not against NK-insensitive P815 cells. An increased level of IL-12 was observed in the serum of mice treated with Virulizin. IL-12 mRNA and protein levels were also increased in peritoneal macrophages isolated from Virulizin-treated mice. Moreover, Virulizin-induced cytotoxic activity of NK cells isolated from the spleen was abolished when an IL-12 neutralizing antibody was co-administered. In addition, depletion of macrophages in mice significantly impaired Virulizin-induced NK cell cytotoxicty. Taken together, the results suggest that Virulizin induces macrophage IL-12 production, which in turn stimulates NK cell-mediated antitumor activity.     

Augmentation of Mouse Natural Killer Cell Activity by Lactobacillus casei and Its Surface Antigens

Lactobacillus casei YIT 9018 (LC 9018) augmented the natural killer (NK) cell activity of spleen cells from inbred BALB/c mice injected intravenously with LC 9018 or intraperitoneally with polyinosinate-polycytidylate. Augmentation of this activity by LC 9018 was also observed in male C3H/He, CBA/N, and C57BL/6 mice. The spleen cells exhibited no cytolytic activity against P815, a cell line insensitive to NK cells. The cytolytic activity of the spleen cells increased 2 days after the injection of 250 μg of LC 9018/mouse, peaked on day 3, and gradually declined thereafter. The increase caused by LC 9018 was also observed in normal and Meth A-bearing mice. In vitro treatment with anti-asialo GM1 antibody plus complement completely-abrogated the LC 9018-augmented murine NK cell activity. The NK activity on the 3rd day after LC 9018 injection was reduced by in vitro treatment with anti-Thy 1.2 monoclonal antibody plus complement to half of that observed when treatment was with complement alone. This suggests that there were two populations of NK cells in the spleen cell suspension derived from LC 9018-treated mice. One population was asialo GM1-positive and Thy 1-negative, the other was asialo GM1-positive and Thy 1-positive.     

Role of natural killer cells in the modulation of primary antibody production by purine nucleosides and their analogs.

Previous results from this laboratory demonstrated that treatment of mice with the adenosine analog tubercidin (Tub) reduced natural killer (NK) cell activity while stimulating antibody production whereas the deoxyadenosine analog, 2-fluoroadenine arabinoside-5'-monophosphate (FaraAMP), produced opposite effects; i.e., it stimulated NK cell activity at doses that inhibited antibody formation (Cancer Res. 48, 4799, 1988). Since NK cells have been reported to play a suppressor role in immunoglobulin induction, it was hypothesized that the actions of Tub and FaraAMP on antibody production occurred secondary to their opposing effects on NK cells. To test this hypothesis, abilities of these nucleoside analogs to modulate primary antibody response to sheep red blood cells were evaluated in a C57BL/6 mutant mouse lacking NK cell activity (the beige mutation. C57BL/6-bg/bg). As previously found with C3H/He mice. NK cell activity was inhibited (Tub, doses 2-6 mg/kg/day for 3 days) or stimulated (FaraAMP, doses 75-250 mg/kg/day for 3 days) in heterozygous mice C57BL/6-bg/+. In support of the hypothesis, these nucleosides had no effect on primary antibody formation in the homozygous mutant mice at doses that clearly stimulated (Tub) or inhibited (FaraAMP) this immune response in heterozygous C57BL/6-bg/+ animals. This results was corroborated in C57BL/6 wild-type mice by abrogation of NK cell activity using a monoclonal antibody to the NK cell surface glycophisingolipid, ganglio-n-tetraosylceramide. We conclude that under the conditions of drug administration, modulation of primary antibody formation by Tub and FaraAMP in mice occurs indirectly via NK cells. Similar experiments using the potent ADA inhibitor, deoxycoformycin, indicated that its enhancement of primary antibody formation is independent of NK cell activity.     

Anti-stress effects of carnosine on restraint-evoked immunocompromise in mice through spleen lymphocyte number maintenance

Carnosine (β-alanyl-L-histidine), a naturally occurring dipeptide, has been characterized as a putative neurotransmitter and serves as a reservoir for brain histamine, which could act on histaminergic neurons system to relieve stress-induced damages. However, understanding of the role of carnosine in stress-evoked immunocompromise is limited. In this study, results showed that when mice were subjected to restraint stress, spleen index and the number of spleen lymphocytes including Natural Killer (NK) cells were obviously decreased. Results also demonstrated that restraint stress decreased the cytotoxic activity of NK cells per spleen (LU(10)/spleen) while the activity of a single NK cell (LU(10)/10(6) cells) was not changed. However, oral administration of carnosine (150 and 300 mg/kg) increased spleen index and number of spleen lymphocytes (including NK cells), and elevated the cytotoxic activity of NK cells per spleen in restraint-stressed mice. These results indicated that carnosine ameliorated stress-evoked immunocompromise through spleen lymphocyte number maintenance. Carnosine was further found to reduce stress-induced elevation of plasma corticosterone level. On the other hand, results showed that carnosine and RU486 (a glucocorticoids receptor antagonist) treatment prevented the reduction in mitochondrion membrane potential and the release of mitochondrial cytochrome c into cytoplasm, increased Bcl-2/Bax mRNA ratio, as well as decreased terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells in spleen lymphocytes of stressed mice. The results above suggested that the maintenance of spleen lymphocyte number by carnosine was related with the inhibition of lymphocytes apoptosis caused by glucocorticoids overflow. The stimulation of lymphocyte proliferation by carnosine also contributed to the maintenance of spleen lymphocyte number in stressed mice. In view of the elevated histamine level, the anti-stress effects of carnosine on restraint-evoked immunocompromise might be via carnosine-histamine metabolic pathway. Taken together, carnosine maintained spleen lymphocyte number by inhibiting lymphocyte apoptosis and stimulating lymphocyte proliferation, thus prevented immunocompromise in restraint-stressed mice.     

Mycoplasma pulmonis infection augments natural killer cell activity in mice

The goal of this study was to determine if experimental Mycoplasma pulmonis infection augmented splenic natural killer (NK) cell activity in mice. A 4 hour 51Cr-release in vitro assay using YAC-1 tumor target cells was employed to measure splenic NK cell activity in C57BL/6J mice infected intraperitoneally with M. pulmonis and in uninfected controls. Transient augmentation of the NK cells was observed, peaking at day 3 postinoculation (PI) and gradually returning to normal levels by day 10 PI. Selective depletion studies showed that the cells responsible for killing target cells were NK cells. They were nonadherent to nylon wool, not susceptible to Thy-1.2 antibody and susceptible to asialo GM1 ganglioside antibody. Inadvertent augmentation of the NK cell system due to M. pulmonis infection may complicate the interpretation of research data, especially in immunology and cancer studies.     

Generation of monoclonal antibodies blocking cytotoxic reactions by human NK clones: further characterization of a 40/80-kDa target cell receptor

To study NK target antigen(s), mice were immunized with pooled cells from five human hematopoietic cell lines (K562, MOLT4, JM, CEM, U937) known to be susceptible to Natural Killer activity. Cells fusions were performed and 4 out of approximately 2000 hybridoma supernatants were selected because of their ability to block cytotoxic reactions between a human NK clone (termed JT9) and MOLT4 cells. Functional characterization of the four monoclonal antibodies (Mabs) indicated that individual treatment of each immunizing target cells resulted in a decreased cytotoxicity. This inhibition was very specific because it was exclusively observed when three clones, JT9, JT10, and JT11, which express the same clonotypic structure (NKTa), were used as effector cells. Parallel and sequential immunoprecipitations showed that the four reagents termed anti-TNKtar 1, 2, 3, and 4 were directed at the same 40/80-kDa heterodimeric structure previously identified by anti-TNKtar Mab. However, cross-blocking experiments indicated that TNKtar and TNKtar 1-4 represent two distinct epitopic clusters. Finally, it was shown that anti-TNKtar 1-4 recognition sites are either identical or closely related to that of an additional antibody termed 4F2. Together, the present data strengthen the hypothesis that the activation antigen recognized by these series of Mab serves as a target cell receptor for at least a minor population of NK active lymphocytes.     

Changes of cell mediated immunity in malignant ovarian tumor patients after operation

OBJECTIVES: The authors discuss upon the changes in the two cell types involved in cell mediated immunity (Killer and Natural Killer) as a result of operation in malignant ovarian tumor atients. METHODS: They study the preoperative and postoperative cell mediated immunity of 28 malignant cystadenocarcinoma cases (FIGO stage I/a-III/c). To determine the maximum K and NK cell activity they used the kinetic model of cytotoxicity enzyme. RESULTS AND CONCLUSIONS: They conclude that operation of malignant ovarian tumors had no significant influence on K and NK cell activity. They hypothesize that unchanged cell mediated immunity seems to be independent of malignant tumors, especially in these conditions. We need further information about this change of cell mediated immunity.     

Regulation of natural killer cell activity by anti-I-region monoclonal antibodies

The effects of a monoclonal antibody directed against immune response gene products on mouse NK activity were examined. In vivo administration of an anti-I-A^k antibody to C3H/He (H-2^k) mice modulated their peritoneal cell (PC) and spleen cell (SC) natural killer (NK) activity against YAC-1 lymphoma target cells in vitro. No such effect was observed when BALB/c (H-2^d) mice were treated with this antibody. Administration of anti-I-A^k antibody to mice before and after infection with Toxoplasma or treatment with poly(I:C) leads to suppression of NK activity in comparison to NK activity of mice infected with Toxoplasma or injected with poly(I:C) alone. A similar treatment regimen with M5/114 antibody which reacts with I-A^b, I-A^d, I-E^d, and I-E^k molecules resulted in decreased NK activity in B10.D2 (H-2^d) but not in B10.BR (H-2^k) mice. Serum and cell culture supernatant interferon (IFN) concentrations were not altered as a result of anti-I-A^k treatment. Removal of adherent cells did not restore NK activity of anti-I-A^k-treated Toxoplasma-infected mice to levels obtained with mice infected with Toxoplasma. In contrast, depletion of Ly 2.1⁺ cells from nylon-wool nonadherent SC of mice treated with anti-I-A^k antibody, before and after infection with Toxoplasma, resulted in restoration of NK activity to the same level as that observed in Toxoptasma-infected mice.     

Physiologic modulation of natural killer cell activity as an index of Alzheimer's disease progression

Patients with Alzheimer's disease (AD) are characterized by an altered sensitivity to cortisol-mediated modulation of circulating lymphocytes. Longitudinal studies are needed to address the clinical applicability of these abnormalities as prognostic factors. Therefore, we designed a longitudinal study to address the clinical applicability of physiologic modulation of Natural Killer (NK) cell activity as a prognostic factor in AD. NK activity was assessed as baseline measurement and in response to modulation by cortisol at 10(-6)M. To verify the immunophysiological integrity of the NK cell population, we tested augmentation of NK cytotoxicity by human recombinant interleukin (IL)-2 (100 IU/ml) as control. The response to modulation by cortisol or by IL-2 was significantly greater in patients with AD. Based on change in the Mini-Mental State score at entry and at 18 months, patients with AD could be assigned to a "fast progression" (Delta > 2 points) or to a "slow progression" group (Delta 相似文献   

Expression of asialo GM1 and other antigens and glycolipids on natural killer cells and spleen leukocytes in virus-infected mice

The sensitivities of mouse natural killer (NK) cells to various antisera and complement were analyzed at different time points after acute lymphocytic choriomeningitis virus infection. Under these conditions NK cell activity peaks 3 days and virus-specific cytotoxic T cell activity 7 days after infection. The sensitivity of the cytotoxic activities to antibodies to asialo GM1 (AGM1), NK 1.2 alloantigen, and Ly 5 was in the order endogenous NK greater than day 3 NK greater than day 7 NK. Day 7 cytotoxic T cells were more resistant than day 7 NK to anti-AGM1 and to anti-NK 1.2, but more sensitive to anti-Ly 5. This decreased sensitivity of activated NK cells to antibodies and C' was examined in more detail for the AGM1 antigen. Antibody to AGM1 completely depleted NK cell activity in control, but not in day 3 lymphocytic choriomeningitis virus infected mice. However, mice treated before infection with antibody did not generate NK cell activity 3 days after infection. The mechanisms of the decreased sensitivity of activated NK cells to antibody to AGM1 was examined. High levels of antibody depleted activity, indicating that the effectors were not devoid of AGM1. Biochemical analyses of spleen leukocytes revealed marked increases in sialic acid, gangliosides, and neutral glycosphingolipids, including AGM1 in the order day 7 greater than day 3 greater than endogenous. Antibody to AGM1 was absorbed out by leukocytes in the order day 7 greater than day 3 greater than endogenous. Flow cytometry (FACS) analyses revealed marked shifts in the frequency and intensity of staining of cells with antibody to AGM1 in the order day 7 greater than day 3 greater than endogenous. All endogenous NK cell activity and all the large granular lymphocytes were associated with the brightest 5% of the total spleen leukocyte population. Day 3 and day 7 NK cell activity was also located in cells sorted by using the gate settings for the top 5% endogenous cells. However, there were marked increases in the number of the very bright cells in the order day 3 greater than day 7 greater than endogenous. These cell numbers correlate with the level of NK cell activity in these fractions. Thus, the decreased sensitivity of activated NK cells to antibody to AGM1 is not due to decreased expression of AGM1 on NK cells, but to a competition for antibody by greatly increased levels of AGM1 in infected spleen leukocytes.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cells with natural killer activity in the cerebrospinal fluid of normal mice and athymic nude mice with acute Sindbis virus encephalitis

Sindbis virus causes an acute, nonfatal inflammatory encephalitis in weanling BALB/c mice. Mononuclear inflammatory cells are present in the cerebrospinal fluid (CSF) as well as in the parenchyma of the brain. Both aspects of this inflammatory response were eliminated by treatment with cyclophosphamide. Athymic nude (nu/nu) mice developed no inflammation in the brain, but did develop a CSF pleocytosis that peaked on day 2 after infection. The time course of the appearance of cells in the CSF was earlier in nu/nu mice than their heterozygote (nu/+) littermates. The pleocytosis in nu/nu mice reached a peak on day 2, whereas in nu/+ mice the peak was on day 4, as it is in normal BALB/c mice. To determine whether some of the CSF cells in nu/nu mice may be natural killer (NK) cells, NK activity was measured in a 4-hr assay by using a YAC-1 target cell. NK cell activity in the spleen and peripheral blood was induced by infection with Sindbis virus in nu/nu mice with a similar time course to that of nu/+ mice (peak 1 day after infection). CSF from nu/nu mice had NK activity present 2 days after infection that was greater than that present in either the peripheral blood or spleen. BALB/c and nu/+ mice had insufficient cells present for assay at day 2, but BALB/c mice had NK activity present in the CSF 3 and 5 days after infection that exceeded that in the peripheral blood or spleen. Brain interferon was detectable on day 1 in nu/nu mice, but not until day 2 in nu/+ mice even though the amounts of brain virus were the same in the two groups at all time points. It is concluded that cells with NK activity contribute to the CSF pleocytosis induced by acute Sindbis virus encephalitis.     

黄芪含药血清对NK细胞活性及KLRK1表达的影响

目的：探讨黄芪含药血清对自然杀伤（NK）细胞活性及杀伤细胞凝集素样受体K1（KLRK1）表达的影响。方法：SD大鼠灌胃不同剂量的黄芪水煎剂制备黄芪含药血清。NK92MI细胞与不同剂量黄芪含药血清及对照血清孵育12h后,采用乳酸脱氢酶释放测定法检测NK细胞对靶细胞YAC-1的杀伤活性,采用qPCR和western blot检测KLRK1 mRNA和蛋白表达。结果：不同浓度黄芪含药血清刺激12h后NK细胞杀伤活性明显增强,KLRK1表达显著升高。结论：黄芪含药血清能活化NK细胞,其机制可能与其激活KLRK1有关。     

Regulation of APO-2 ligand/trail expression in NK cells-involvement in NK cell-mediated cytotoxicity.

Apo-2L is a new member of the tumour necrosis factor (TNF) family shown to induce apoptosis in a number of tumour cell lines. Apo-2L mRNA is expressed by numerous human tissues. Here we report that Apo-2L is expressed and utilized by human Natural Killer (NK) cells. NK cells were shown to express surface Apo-2L in response to interleukin 2 (IL-2) activation, and this response was restricted to the CD3(-)population of the NK cells. Apo-2L mRNA and intracellular Apo-2L were present in both CD3(-)and CD3(+)NK cells; however, increased expression in response to IL-2 was only observed in CD3(-)CD56(+)cells. Also, IL-2-activated NK cells were shown to utilize membrane-bound Apo-2L in mediating lysis of Jurkat cells. Furthermore, Apo-2L-induced apoptosis of Jurkat cells was more rapid than FasL-induced apoptosis, indicating an important and distinct role for Apo-2L in apoptotic cell destruction. In conclusion, we report that NK cells express Apo-2L and that IL-2 activated CD3(-)NK cells utilize the Apo-2L pathway in mediating target cell lysis.     

Immunodeficient mice have elevated numbers of NK cells in non-lymphoid tissues

Natural killer (NK) cells are an important part of the innate immune response. They have the ability to recognize and kill many types of tumor cells and promote immunity against intracellular pathogens. In this study, we analyzed the in situ localization of NK cells within wildtype and immunodeficient mice using a novel in situ analysis method. We have identified NK cells in tissues of B6 and B6.Rag1(-/-) mice and demonstrated an increase in the percentage of NK cells and the total number of NK cells in the lung and liver of immunodeficient mice. This increase was not due to an increase in NK cell activation. This study describes a means to identify NK cells within complex tissue environments, and the increase in NK cells in non-lymphoid tissues may explain much of the increased NK cell activity observed in T-cell-deficient mice.     

Synthesis of a prolactin-like peptide by natural killer cells: positive regulation by CD16 and exogenous prolactin.

We have previously shown that Prolactin (PRL) activates the native and the in vitro acquired cytotoxicity and the DNA synthetic activity of Natural Killer (NK) cells. Here we show that the supernatant and the cell lysate of NK cells express a 35S-labelled 50 kDa peptide specifically immunostained by two different PRL-antisera. The supernatant of NK cells was biologically active in a Nb2 assay and the activity could be adsorbed by an anti-PRL antiserum. The production of the PRL-like peptide only occurred when NK cells were isolated through binding to immobilized immunocomplexes, the biological ligand for CD16, and was positively modulated by exogenous PRL. These results indicate that PRL, produced by NK cells following stimulation, may act in an autocrine fashion to maintain and/or activate the NK cell function.     

Induction of natural killer cell responses by ectromelia virus controls infection

Natural killer (NK) cells play a pivotal role in the innate immune response to viral infections, particularly murine cytomegalovirus (MCMV) and human herpesviruses. In poxvirus infections, the role of NK cells is less clear. We examined disease progression in C57BL/6 mice after the removal of NK cells by both antibody depletion and genetic means. We found that NK cells were crucial for survival and the early control of virus replication in spleen and to a lesser extent in liver in C57BL/6 mice. Studies of various knockout mice suggested that gammadelta T cells and NKT cells are not important in the C57BL/6 mousepox model and CD4+ and CD8+ T cells do not exhibit antiviral activity at 6 days postinfection, when the absence of NK cells has a profound effect on virus titers in spleen and liver. NK cell cytotoxicity and/or gamma interferon (IFN-gamma) secretion likely mediated the antiviral effect needed to control virus infectivity in target organs. Studies of the effects of ectromelia virus (ECTV) infection on NK cells demonstrated that NK cells proliferate within target tissues (spleen and liver) and become activated following a low-dose footpad infection, although the mechanism of activation appears distinct from the ligand-dependent activation observed with MCMV. NK cell IFN-gamma secretion was detected by intracellular cytokine staining transiently at 32 to 72 h postinfection in the lymph node, suggesting a role in establishing a Th1 response. These results confirm a crucial role for NK cells in controlling an ECTV infection.     

Modulation of natural killer cytotoxicity by muramyl dipeptide and trehalose dimycolate incorporated in squalane droplets

Summary The effect on natural killer (NK) cytotoxicity of splenic cells from BALB/c mice pretreated i. v. with squalane-in-water preparations of muramyl dipeptide (MDP), trehalose dimycolate (TDM), or the combination of MDP-plus-TDM was investigated. MDP or TDM augmented the NK cytotoxicity which peaked 48 h after the pretreatment whereas the combination of MDP and TDM induced an inhibition of the NK activity. Infection with influenza virus, a potent stimulator of NK cells, after the pretreatment with biological response modifiers resulted in a markedly enhanced NK activity on day 2 in MDP and control groups. Mice pretreated with TDM or the combination of MDP and TDM showed only moderate NK activity which peaked on day 3 after influenza infection. The NK activity was susceptible to asialo GM₁ and complement treatment. The cytotoxicity of MDP-plus-TDM cells could be significantly enhanced after treatment with anti-macrophage monoclonal antibody and complement. NK activity induced by MDP or TDM was reduced by mixing MDP-plus-TDM cells. Addition of adherent cell-depleted MDP-plus-TDM suspension to MDP or TDM cells had a NK restorative effect. Splenic cells from mice pretreated 2 days earlier with MDP or TDM, but not MDP-plus-TDM, generated enhanced levels of luminol-dependent chemiluminescence.