Increase In Natural Killer Activity Research Articles

Interleukin 4 (IL-4) Blocks the IL-2-Induced Increase in Natural Killer Activity and DNA Synthesis of Decidual CD16−CD56brightNK Cells by Inhibiting Expression of the IL-2 Receptor α, β, and γ

The natural killer (NK) activity and DNA synthesis of decidual CD16−CD56brightNK cells were markedly elevated by treatment with interleukin 2 (IL-2). IL-4 did not affect NK activity or DNA synthesis of decidual CD16−CD56brightNK cells, but inhibited the IL-2-induced NK activity and DNA synthesis in a dose-dependent manner. Flow cytometry of decidual mononuclear cells cultured in IL-2 or IL-4 or both IL-2 and IL-4 demonstrated IL-4 inhibition of the expression of the IL-2 receptor α (IL-2Rα), IL-2Rβ, and IL-2Rγ on decidual CD16−CD56brightNK cells. This suggests that IL-4 blocks the IL-2-induced NK activity and DNA synthesis of decidual CD16−CD56brightNK cells by inhibiting the expression of IL-2Rα, IL-2Rβ, and IL-2Rγ.

Time course of the cytotoxicity of blood mononuclears in patients with bladder cancer during endolymphatic immunotherapy with lymphokine-activated killers and recombinant interleukin-2

A specific stimulation of mononuclear cellsin vivo was observed after 3 or 4 endolymphatic injections of autologous lymphokine-activated killers and recombinant interleukin-2 in male patients with disseminated bladder cancer. This activation presented as an increase of the cytotoxicity of mononuclears towards target cells of bladder carcinoma. A statistically reliable increase of natural killer activity was observed, and in one patient a reliable increase of the cytolytic activity of mononuclear cells against Mel-1 target cells. After 1 or 2 injections the activity of natural killers increased to 80–90% for an initial level of 23–50%.

Mycoplasma arthritidis mitogen up-regulates human NK cell activity.

While the effects of superantigens on T lymphocytes are well characterized, how superantigens interact with other immune cells is less clear. This report examines the effects of Mycoplasma arthritidis mitogen (MAM) on human natural killer (NK) cell activity. Incubation of peripheral blood mononuclear cells (PBMC) with MAM for 16 to 20 h augmented NK cytotoxicity (against K562) in a dose-dependent manner (P < or = 0.05). Superantigen-dependent cellular cytotoxicity, an activity of superantigen-activated cytotoxic T cells, was not involved in lysis of K562 cells because the erythroleukemic tumor target cells expressed no class II major histocompatibility complex by fluorescence-activated cell sorter analysis. Kinetic experiments showed that the largest increase in NK activity induced by MAM occurred within 48 h. Incubation with MAM caused a portion of NK cells to become adherent to tissue culture flasks, a quality associated with activation, and augmented NK activity was found in both adherent and nonadherent subpopulations. Experiments using cytokine-specific neutralizing antibodies showed that interleukin-2 contributed to enhancement of the NK activity observed in superantigen-stimulated PBMC. Interestingly, MAM was able to augment NK lysis of highly purified NK (CD56+) cells in the absence of other immune cells in 9 of 12 blood specimens, with the augmented lytic activity ranging from 110 to 170% of unstimulated NK activity. In summary, data presented in this report show for the first time that MAM affects human NK cells directly by increasing their lytic capacity and indirectly in PBMC as a consequence of cytokines produced by T cells. Results of this work suggest that, in vivo, one consequence of interaction with superantigen-secreting microorganisms may be up-regulation of NK lytic activity. These findings may have clinical application as a means of generating augmented NK effector cells useful in the immunotherapy of parasitic infections or neoplasms.

Natural killer cell cytotoxicity in elderly humans after influenza immunization.

Previous studies have reported that human natural killer (NK) cytotoxicity can be augmented by either in vitro stimulation with influenza virus antigens or in vivo administration of killed influenza vaccine. The study demonstrating the latter conclusion reported an increase in NK cytotoxicity lasting for 4 weeks postvaccination in young subjects. We initiated our study to determine if a similar increase in NK activity was observed in an elderly population after immunization with the 1992-1993 influenza vaccine. NK activity of 34 elderly (mean age, 77.3 years) was determined at 3 time points: prevaccination, 4 to 6 weeks postvaccination, and 5 to 6 months after vaccination. In contrast to the results of the previous study, the NK cytotoxicity of our elderly subjects was not augmented by the influenza vaccine at any time tested. We also determined the number of CD56+ cells in whole-blood samples at each of the time points and found that there is no change in NK cell number after influenza vaccination.

Characterization of natural killer cell activity in Macaca nemestrina.

Natural killer (NK) cell activity was evaluated in three groups of Macaca nemestrina that varied with respect to SAIDS D retrovirus serotype 2 (SRV-2/W) and viremic status. Target cells used were Raji and K562 cells. No significant differences (ANOVA) in mean NK activity were detected among the three groups of animals studied. Using Raji targets, mean LU30/106 ± SEM was 6.3 ± 1.6 for seronegative (V-Ab-) animals, 7.3 ± 1.5 for seropositive (V-Ab+) animals, and 10.2 ± 3.5 for persistently viremic (V + Ab-) animals. Using K562 targets, mean LU30/106 was 7.6 ± 1.7 for seronegative (V-Ab-) animals, 6.5 ± 2.5 for seropositive (V-Ab+) animals, and 5.1 ± 1.9 for persistently viremic (V+Ab-) animals. Percentage blood CD16+ and CD8+cells also were not different in the three groups of animals. NK activity did not always correlate with percentage of CD16+ or CD8+ cells in peripheral blood at the time the assays were done. In persistently viremic animals, there was a strong positive correlation between percent CD16+ and CD8+ cells and NK activity using K562 cells but not Raji cells. Depletion experiments indicated that lysis was mediated by both CD8+ and CD16+ cells with both Raji and K562 cells. However, Raji targets were a better indicator of killing mediated by CD16+ cells. Our studies indicate that M. nemestrina may be classified as high or low responders with regard to NK activity, and there was no correlation with SRV-2/W viral or antibody status. Additionally, our results suggested that group housing of M. nemestrina was usually associated with increased NK activity. In conclusion, studies of NK activity in M. nemestrina should consider target cells used, phenotype of effectors, endogenous (high or low) levels of NK activity in individual animals, and housing conditions. © 1996 Wiley-Liss, Inc.

Role of natural effector cells in the prevention of radiation-induced leukemogenesis

Four once-weekly exposures of 225 rads (R) of whole body X-irradiation causes a high incidence of lymphoma in C57BL/6 (C57) mice. The role of natural effector cells in radiation-induced leukemogenesis was investigated. Activity of natural killer (NK) and natural cytotoxic (NC) cells was depressed in irradiated mice over a prolonged period. Transplantation of bone marrow (BM) cells from normal C57 mice to irradiated mice restored their NK responses and prevented development of lymphoma. The effect of beige BM cell transfer to irradiated mice was not clear. Unlike short-term (4-hour) assay, results of long-term (20-hour) assay suggest partial restoration of NK and full restoration of NC activity in irradiated mice. Treatment of irradiated mice with polyinosinic: polycytidillic acid (poly I:C) increased NK activity and lymphoma resistance. Administration of small repeated doses of poly I:C to irradiated mice significantly prevented the development of lymphoma as well as significantly prolonging overall survival time in irradiated mice. These observations indicate that natural effector cells mediate resistance to radiation-induced leukemogenesis.

Natural killer cell activity in patients with invasive cervical carcinoma: importance of a longitudinal evaluation in follow-up.

To analyze longitudinally the basal natural killer cell activity in patients with invasive cervical carcinoma, the natural cytotoxicity was related to the most important known prognostic factors, and evaluated with respect to the clinical outcome of cervical disease. Forty-six patients with histologically proven invasive cervical carcinoma treated and followed at the Institute of Gynecology and Obstetrics, Ancona University, Salesi Hospital, were consecutively recruited from 1989 to 1992 and included into the study. For immunologic investigation, natural killer cell activity and peripheral blood T-lymphocyte subsets were tested before primary treatment and during the follow-up period, every 6 months. Natural killer activity was determined by target cell retention of the fluorescent dye carboxyfluorescein diacetate; the K 562 cell line was used as target cells. A significant inverse relationship was observed between natural killer activity and disease stage (p = 0.001); patients with stage IV disease had the lowest level of natural cytotoxicity. The reduction of natural cytotoxicity was not accompanied by any alteration of lymphocyte distribution. The longitudinal analysis showed an increase of natural killer activity after surgical removal of the tumor, persisting during the follow-up, but all the 9 patients who recurred showed, at the time of disease recurrence, a significant decrease of their natural cytotoxic potential. Natural killer cell activity seems to be a functional index of immune status, significantly related to the stage and the clinical outcome of disease.

Drug-Mediated Changes in the Susceptibility of Human Lymphoblastoid B Cells to NK-Mediated Cytolysis: Studies with a Triazene Compound

Previous studies have shown that treatment of leukemia-bearing mice with triazene compounds results in a profound alteration of the immunological properties of leukemic cells. These cells become highly immunogenic and susceptible to natural immunity (NI). Moreover, in a pilot clinical study, dacarbazine was found to suppress bone marrow blasts in patients with acute non-lymphoblastic leukemias. The cytotoxic mechanism involved could be of biochemical and immunological origin as well. Therefore experiments were carried out to test whether triazenes could influence the susceptibility of blast cells to human NI effector lymphocytes (represented, at least in part, by NK cells). The results obtained with target Epstein-Barr virus (EBV)-immortalized B cells and effector cells of different donors, showed that: (a) multiple in vitro treatments of lymphoblastoid cells with methyl-triazene-benzoic acid (MTBA, a triazene compound active in vitro), gave origin to lines that were more resistant than the parental lines to the antitumor effects of MTBA; (b) MTBA-treated lines were more susceptible (37.5% of cases), or less susceptible (31.2% of cases) to NI than parental cells. Effector lymphocytes of various donors recognized different changes in susceptibility to natural killer (NK)-mediated lysis; (c) treatment of parental or MTBA-treated lines with interferon-beta reduced target cell susceptibility to NK-mediated cytolysis, but increased NK activity and lymphoblast chemosensitivity to MTBA.

Inhibition of natural killer cell activity by dietary lipids

Natural killer (NK) cells are a subset of cytotoxic lymphocytes found mainly in blood and the spleen. NK cells play a role in natural immunity to microbes, viruses and tumor cells and are involved in the rejection of grafts. The present study investigated the effects of diets containing oils rich in saturated fatty acids, mono-unsaturated fatty acids, n-6-poly-unsaturated fatty acids (PUFA) or n-3-PUFA on the NK cell activity and on the lymphokine-activated killer (LAK) cell activity of rat spleen lymphocytes. Weanling rats were fed for 10 weeks on a low-fat (LF) diet (∼ 2% fat by weight) or on 1 of 5 high-fat (HF) diets, which contained 20% (by weight) hydrogenated coconut oil (HCO), olive oil (OO), safflower oil (SO), evening primrose oil (EPO) or menhaden (fish) oil (MO). Each of the HF diets suppressed the NK activity of freshly prepared spleen lymphocytes compared with the LF diet; cells from the MO-fed rats exhibited the lowest NK activity. Culture with IFNα for 3 h increased the NK activity of spleen lymphocytes from all animals, except those fed the OO diet; the increase in NK activity varied from 20% (LF) to 50% (MO). Although feeding the OO, EPO or MO diets resulted in lower IFN α-stimulated NK activity than that obtained by feeding the LF diet, the only consistent significant difference was the lower activity of the cells from the OO-fed rats compared with those from the LF-fed rats. LAK cells were generated by culture of spleen lymphocytes with ConA for 24 h followed by IL-2 for 72 h. All of the HF diets decreased LAK cell activity; statistically significant effects were observed for lymphocytes from rats fed the MO diet compared with those from rats fed the LF-fat diet. These observations show that dietary PUFA, particularly those of the n-3 family inhibit NK cell activity. This may be useful in prolonging graft survival, but may also decrease the ability of the host to destroy invasive microbes, viruses and tumor cells.

Interferon as adjunctive treatment for non-metastatic renal cell carcinoma

To investigate the effect of recombinant alpha 2b-interferon therapy on natural killer (NK) activity and antibody-dependent cell-mediated cytotoxicity (ADCC) in the peripheral blood in patients with renal cell carcinoma who had undergone radical nephrectomy. Between January 1988 and June 1989, 20 patients (14 men and six women, mean age 59 years, range 43-80) received interferon (IFN) therapy following radical nephrectomy for renal cell carcinoma. Thirteen patients had stage I disease, one had stage II and six had stage III; none had metastases. There was a significant increase in NK activity at 5 and 7 months after starting IFN therapy but there was no increase in ADCC. Low doses of IFN administered long-term increased NK activity in patients with renal cell carcinoma. This finding should be helpful in designating protocols for randomized studies of post-operative IFN administration as adjuvant therapy.

Thymic Hypoplasia and T-Cell Deficiency in Ectodermal Dysplasia: Case Report and Review of the Literature

Ectodermal dysplasia is a heterogeneous disorder that includes a constellation of congenital malformations occasionally associated with mild to moderate immune dysfunction. In this report, we describe a female infant with ectodermal dysplasia who was found to have thymic hypoplasia but no other phenotypic features of the DiGeorge anomalad. She experienced Candida parapsilosis sepsis at 1 week of age and a skin infection with Mycobacterium chelonii at 6 months. The numbers of blood B cells were normal and serum immunoglobulins normal to slightly reduced, but serum antibody responses of all immunoglobulin isotypes to protein immunogens were absent. Blood T cells were profoundly reduced and proliferative responses of T cells to mitogens were blunted. In contrast, there was an increased number of natural killer (NK) cells and increased NK activity in the blood. Over the first year of life, some of the immunodeficiencies resolved. Although the numbers of blood T cells (17% of total lymphocytes) remained low, proliferative responses to mitogens normalized and specific antibody responses improved. It seems likely that the thymic hypoplasia in this case was due to a paucity of ectodermal elements in the developing thymus, and that the immune defects were largely secondary to that event. In that respect, this human model of ectodermal dysplasia and thymic hypoplasia resembled the ectodermal/thymic defects found in the nude mouse.

IN VITRO ENHANCEMENT OF NATURAL KILLER CELL ACTIVITY BY BCG AND THE ANTAGONISTIC INHIBITION OF THE SUSCEPTIBILITY OF K562 CELLS TO LYSIS BY PERIPHERAL BLOOD LYMPHOCYTES IN PATIENTS WITH URINARY BLADDER TUMOR

The effect of bacillus Calmette-Guerin (BCG) on the natural killer (NK) activity of peripheral blood lymphocytes (PBL) and the susceptibility of K562 cells to lysis by PBL in patients with urinary bladder tumors (UBT) was evaluated using a 4-h 51Cr release assay. The addition of BCG 0.1-1 mg/ml to the assay increased NK activity. In contrast, BCG at higher concentrations (10 mg/ml) reduced NK activity. This effect of BCG was also observed in healthy donors. Pretreatment of PBL with BCG 0.1-1 mg/ml also resulted in increased NK activity, while higher concentrations of BCG depressed it. Treatment of K562 cells with BCG 1-10 mg/ml for 3 hours reduced their susceptibility to lysis by PBL. Kinetic studies showed that the reduced susceptibility became apparent 3 hours after initiation of culture of K562 cells with BCG and lasted 12 hours. The susceptibility of BCG-treated K562 cells to lysis by purified NK cells and lymphokine activated killer (LAK) cells was also reduced. Both live and dead BCG exerted an inhibitory effect on the target cells. The effector-to-target binding assay demonstrated that treatment with BCG reduced the number of PBL conjugates with K562 cells. These results indicate that BCG increases the NK activity of PBL, while rendering K562 cells resistant to PBL lysis by inhibiting the effector-to-target binding. BCG at lower concentrations (0.1-1 mg/ml) may be useful in patients with UBT. The possible mechanisms responsible for the effects of BCG on K562 cells and their possible clinical implications are discussed.

Interferon alpha 2b treatment of cervical intraepithelial neoplasia grade 2: modulation of natural killer cell.

The objective was to evaluate natural cytotoxicity of peripheral blood during interferon treatment in cervical intraepithelial neoplasia grade 2 (CIN2), as index of interferon activity. Twenty-one patients with CIN2, histologically proven, were treated with interferon alpha 2b (Intron A, Sheering-Plough Corp.), in a dose of 3,000,000 units three times per week for 8 weeks self-administered by intramuscular injection. The rate of remission to the interferon treatment was 38.1%. Eight healthy patients had a significant increase in natural killer activity during and after the treatment (p < 0.001), whereas the 13 nonresponder patients remained with low values of natural killer activity. By analyzing the basal natural killer activity before the treatment, the patients with clinicopathologic remission had a significantly higher mean value than nonresponder patients (p = 0.007). Notwithstanding the specimen exiguity, the individual basal natural killer activity seems to be a predictive parameter of interferon treatment response in patients with CIN2.

Natural Killer Cell Cytotoxicity and T-Cell Proliferation Is Enhanced by Avoidance Behavior

Natural killer (NK) cell activity and mitogen-stimulated spleenocyte proliferation were measured in rats exposed to stress in the form of avoidable and unavoidable shock. Rats that could avoid shock exhibited higher NK activity than either unshocked controls or rats that could not avoid shock. The latter were yoked to the avoidance rats and thus received the same number and frequency of shocks as did the avoidance group. The increased NK activity in the avoidance group appears due to a higher number of NK cells in this group as compared with those in the control or unavoidable shock groups. Additionally, NK activity was found to be proportional to avoidance response rate, with a majority of animals exceeding the minimal temporal avoidance requirement. Mitogen-stimulated proliferation of spleenocytes was also increased several fold in the group that could avoid shock as compared with that which could not and controls. The difference in NK activity and mitogen-stimulated proliferation could not be ascribed to differences in cortisol levels. The results indicate that behavior which results in the avoidance of aversive stimuli can lead to significant enhancement of immune system competence.

Measurement of NK activity in effector cells purified from canine peripheral lymphocytes

Natural killer (NK) cells spontaneously lyse a variety of tumor cells in vitro, and are believed to play an important role in host resistance to tumor growth and metastasis in vivo. As part of our work in comparative oncology, we have designed and validated a canine NK cell assay. Of several lymphocyte isolation techniques evaluated, sedimentation of whole blood through a two-step Ficoll/Hypaque gradient ( sp. gr. 1.066 1.119 ) followed by plastic adherence of monocytes resulted in the most pure lymphocyte population (> 95% lymphocytes). Of four cell lines evaluated as targets in the NK assay, a canine thyroid adenocarcinoma (CTAC) cell line was determined to be most sensitive, and a lymphoblastoid (CT45-S) cell line was determined to be most resistant to NK lysis. A 15 h effector-target incubation period using these targets resulted in reproducible measurement of cell specific lytic activity. Passage of canine lymphocytes through nylon wool columns did not result in a significant increase in NK activity. A final sedimentation of purified lymphocytes through a 45 50% Percoll gradient concentrated NK activity into a single band of lymphocytes. Lymphocytes forming conjugates with CTAC target cells were 5.5–6.5 μm in diameter, and were characterized by a reniform nucleus and varying numbers of electron-dense cytoplasmic granules.

Self-discrepancy and natural killer cell activity: immunological consequences of negative self-evaluation.

The study tested whether self-discrepancy theory could account for changes in natural killer (NK) cell activity after exposure to self-referential stimuli. Anxious, dysphoric, and control Ss were pretested and 1 month later covertly exposed to their own self-guides as well as those of another S. Blood samples were drawn for analysis of NK cytotoxicity and cortisol. The dysphoric Ss manifested the greatest actual:ideal discrepancy, whereas the anxious Ss manifested the greatest actual:ought discrepancy. Content analysis of written responses showed that activating discrepancies induced specific negative states; priming discrepancies also increased cortisol for the anxious Ss. NK activity was lower after self-referential priming for both distressed groups, particularly the anxious Ss. The control Ss showed a trend toward increased NK activity after self-referential priming. The study represents the 1st experimental demonstration that negative self-evaluation can alter immune responses.

Increase in peripheral natural killer cell activity in patients with autoimmune thyroid disease.

Changes in the activity and number of natural killer (NK) cells in peripheral blood in patients with autoimmune thyroid disease were examined. NK activity was measured in a 4-hr 51Cr-release assay and the number of NK cells was analyzed with FITC-conjugated monoclonal antibodies by use of an automated flow cytometer. NK activity in patients with untreated Graves' disease (n = 25, 39.7 +/- 13.5%, P less than 0.05) and Hashimoto's thyroiditis (n = 18, 41.0 +/- 14.2%, P less than 0.05) was high compared to the activity in non-pregnant controls (n = 61, 32.6 +/- 15.0%). NK activity in patients with postpartum Graves' thyrotoxicosis (n = 11, 48.6 +/- 18.9%) was markedly increased compared to the activity in non-pregnant controls (P less than 0.01) and in postpartum controls (n = 29, 33.8 +/- 15.2%, P less than 0.05), although the mean ages of each group did not differ significantly. Moreover, NK activities in the thyrotoxic state were significantly higher than those in the euthyroid state in the same patients with postpartum Graves' thyrotoxicosis or with postpartum destructive thyrotoxicosis. The number of CD16 positive cells increased in patients with postpartum Graves' thyrotoxicosis. However the number of CD16 and CD57 positive cells were normal in all other groups of patients. These results indicate that an increase of NK activity is associated with exacerbation of autoimmune thyroid disease both in Hashimoto's thyroiditis and in Graves' disease and suggest that NK cells might have an important role for the control of disease activity in autoimmune thyroid disease.

Pidotimod stimulates natural killer cell activity and inhibits thymocyte cell death.

Experiments were performed to analyze the possible effect of the immunomodulating agent Pidotimod (3-L-pyroglutamyl-L-thiazolidine-4-carboxylic acid) on mouse Natural Killer (NK) cell activity and glucocorticoid hormone(GCH)-induced thymocyte apoptosis. The results indicate that in vivo treatment with Pidotimod (200 mg/Kg ip for 5 days) causes a significant increase in NK activity and in vitro treatment produces a significant reduction of dexamethasone-induced thymocyte apoptosis. This inhibition appears to be dose-dependent and is also evident against TPA or Ca(++)ionophore-induced apoptosis.

In vivo biderectional regulation of mouse natural killer (NK) cell cytotoxic activities by Leu-Enkephalin: Reversibility by naloxone

Intraperitoneal injection of Leu-enkephalin (LENK, 10 or 7.5 mg/kg) induced bidirectional modulation of natural cytotoxic activities in spleens of CBA mice (suppression followed by enhancement). NK-cytotoxic activity was more affected than the ADCC. Early suppression of NK activity could be reversed by 4 × M excess of naloxone injected 20 min before LENK, suggesting that the suppression was mediated by opioid receptors. Subsequent increase of NK activity could not be abrogated by naloxone, at least not completely. Naloxone itself decreased NK activity 12 hours after treatment, but enhanced ADCC at 24 and 48 hours. This increase was abrogated by LENK. In addition to functional alterations, LENK also induced phenotypic changes of spleen cells, i.e. a decrease in the percentage of asialo-GM-1 + cells 24 hours posttreatment. There was no correlation between LENK-induced alterations of cytotoxic function and the percentage of cells with NK phenotype (GM-1 +). Thus, LENK modulates cytolytic functions and the phenotype of NK cells in vivo in a complex way, which besides opioid mechanisms may also include non-opioid ones.

Kinetics and Regulation of NK Activity by Interleukin-2 and Interferon in Acute Toxoplasmosis

Natural killer (NK) activity against Toxoplasma gondii tachyzoites and tumour cells during acute toxoplasmosis was investigated using a single-cell NK assay. During the course of infection the percentage of lymphocytes binding tachyzoites and tumour cells did not vary significantly and NK activity was enhanced due to an increase in the specific cytolytic capacity per cell. To determine whether regulatory mechanisms mediated by cytokines might explain the increased NK activity, the kinetics of interleukin-2 (IL-2) and interferon (IFN) production and the correlation between their concentrations and the level of NK activity were analysed at the same time. As the infection progressed NK activity increased in spite of the fact that IL-2 production decreased (except for a small increase during the first day of infection). However, IFN production increased gradually in close temporal and quantitative association with the overall increase in NK activity. These results suggest that T. gondii, via its ability to produce interferon, enhances NK activity against itself and other cells.