Stimulation Of Natural Killer Cell Activity Research Articles

Anti-Inflammatory Effects and Immunomodulatory Efficacy of Unitein (Fermented Glycine max, Panax ginseng, and Chenpi Mixture) in RAW 264.7 Macrophages and Mice Splenocytes along with Component Analysis

Inflammation and the immune system are intricately linked, with the immune system serving as a vital defense mechanism in the human body. Consequently, there is great emphasis placed on the regulation of both the body’s inflammatory response and the immune system. This study investigated the anti-inflammatory properties and immunomodulatory effects of Unitein (fermented Glycine max, Panax ginseng, and chenpi mixture) in both RAW 264.7 macrophages and mice splenocytes while also comprehensively analyzing its components. To this end, the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay was employed to evaluate the cytotoxicity of the samples to RAW 264.7 cells. The Griess assay was utilized to determine nitrite concentrations, while the enzyme-linked immunosorbent assay (ELISA) was employed to assess the levels of inflammation-related cytokines in RAW 264.7 cells and isolated mouse splenocytes. Additionally, quantitative polymerase chain reaction was employed to quantify the mRNA expression of inflammation-related genes in the cells, while the lactate dehydrogenase assay was used to analyze natural killer (NK) cell activity. Our results revealed that Unitein exhibited no toxicity to RAW 264.7 cells at concentrations below 1.5 mg/mL. However, Unitein effectively suppressed the release of proinflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and interferon (IFN)-γ, as well as enzymes COX-2 and iNOS from RAW 264.7 cells, while concurrently promoting the release of anti-inflammatory cytokines IκB-α, IL-10, and IL-4. Furthermore, Unitein inhibited the increase in TNF-α, IL-1β, IFN-γ, IL-12, nuclear factor (NF)-κB p50, NF-κB p65, and iNOS induced by lipopolysaccharides (LPSs) in isolated mouse splenocytes. Notably, Unitein also exhibited the potential to stimulate NK cell activity. Metabolite analysis indicated that Unitein contained more active compounds with anti-inflammatory and immunity-enhancing properties than did unfermented Unitein. This study highlights the potential therapeutic role of Unitein in mitigating inflammation and enhancing immune responses, thereby deepening our understanding of its biological activities and underlying mechanisms. These findings underscore the significance of Unitein as a potential candidate for the development of novel anti-inflammatory and immunomodulatory interventions.

Differential Effects of Yin- and Yang-Chinese Tonifying Herbs on Innate and Adaptive Immunity

The present study investigated the effect of treatment with methanolic extracts of Yin- and Yang-Chinese tonifying herbs on concanavalin A (Con A)/lipopolysaccharide (LPS)-stimulated splenocyte proliferation (adaptive immunity) and natural killer (NK) cell activity (innate immunity) in an ex vivo mouse model. The results indicated that while treatment with most Yin herbal extracts potentiated the Con A/LPS-stimulated splenocyte proliferation, only Yang (but not Yin) herbal extracts stimulated NK cell activity. The differential effects of Yin- and Yang-Chinese tonifying herbs on innate and adaptive immunity are consistent with the Chinese medicine theory which depicts the Yin and Yang functional components of Zheng Qi (vital energy), with the Yang component being responsible for the first line of defense against invading microorganisms (i.e., innate immunity) and the Yin oner serving as a follow-up defensive response (adaptive immunity).

Anti-NKG2A mAb Is a Checkpoint Inhibitor that Promotes Anti-tumor Immunity by Unleashing Both T and NK Cells

SummaryCheckpoint inhibitors have revolutionized cancer treatment. However, only a minority of patients respond to these immunotherapies. Here, we report that blocking the inhibitory NKG2A receptor enhances tumor immunity by promoting both natural killer (NK) and CD8+ T cell effector functions in mice and humans. Monalizumab, a humanized anti-NKG2A antibody, enhanced NK cell activity against various tumor cells and rescued CD8+ T cell function in combination with PD-x axis blockade. Monalizumab also stimulated NK cell activity against antibody-coated target cells. Interim results of a phase II trial of monalizumab plus cetuximab in previously treated squamous cell carcinoma of the head and neck showed a 31% objective response rate. Most common adverse events were fatigue (17%), pyrexia (13%), and headache (10%). NKG2A targeting with monalizumab is thus a novel checkpoint inhibitory mechanism promoting anti-tumor immunity by enhancing the activity of both T and NK cells, which may complement first-generation immunotherapies against cancer.

Protective Effect of Panax notoginseng Root Water Extract against Influenza A Virus Infection by Enhancing Antiviral Interferon-Mediated Immune Responses and Natural Killer Cell Activity.

Influenza is an acute respiratory illness caused by the influenza A virus, which causes economic losses and social disruption mainly by increasing hospitalization and mortality rates among the elderly and people with chronic diseases. Influenza vaccines are the most effective means of preventing seasonal influenza, but can be completely ineffective if there is an antigenic mismatch between the seasonal vaccine virus and the virus circulating in the community. In addition, influenza viruses resistant to antiviral drugs are emerging worldwide. Thus, there is an urgent need to develop new vaccines and antiviral drugs against these viruses. In this study, we conducted in vitro and in vivo analyses of the antiviral effect of Panax notoginseng root (PNR), which is used as an herbal medicine and nutritional supplement in Korea and China. We confirmed that PNR significantly prevented influenza virus infection in a concentration-dependent manner in mouse macrophages. In addition, PNR pretreatment inhibited viral protein (PB1, PB2, HA, NA, M1, PA, M2, and NP) and viral mRNA (NS1, HA, PB2, PA, NP, M1, and M2) expression. PNR pretreatment also increased the secretion of pro-inflammatory cytokines [tumor necrosis factor alpha and interleukin 6] and interferon (IFN)-beta and the phosphorylation of type-I IFN-related proteins (TANK-binding kinase 1, STAT1, and IRF3) in vitro. In mice exposed to the influenza A H1N1 virus, PNR treatment decreased mortality by 90% and prevented weight loss (by approximately 10%) compared with the findings in untreated animals. In addition, splenocytes from PNR-administered mice displayed significantly enhanced natural killer (NK) cell activity against YAC-1 cells. Taking these findings together, PNR stimulates an antiviral response in murine macrophages and mice that protects against viral infection, which may be attributable to its ability to stimulate NK cell activity. Further investigations are needed to reveal the molecular mechanisms underlying the protective effects of PNR and its components against influenza virus A infection.

Enhanced natural killer cell activation by exopolysaccharides derived from yogurt fermented with Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1

Yogurt is generally recognized as a beneficial food for our health, but research into its physiological effects has focused mainly on intestinal dysfunctions such as constipation and diarrhea. We previously found yogurt fermented with Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 (hereafter OLL1073R-1) could reduce risks of catching the common cold and flu in human trials. It was assumed that immunostimulatory exopolysaccharide (EPS) produced from OLL1073R-1 play an important role in this context. However, few studies have examined the immunostimulatory effects of traditional Bulgarian yogurts fermented with different strains of lactobacilli and their metabolites. Therefore, we screened 139 L. delbrueckii ssp. bulgaricus strains and identified OLL1073R-1 as the most robust producer of EPS. This strain was also the only strain that induced the production of IFN-γ in vitro. Oral administration of the EPS or yogurt fermented with OLL1073R-1 and Streptococcus thermophilus OLS3059 (OLL1073R-1 yogurt) augmented natural killer (NK) cell activity and induced IFN-γ production in spleen cells in mice, whereas 2 other yogurts fermented with other strains had no effect on NK cell activity. Cellular preparations of the OLL1073R-1 strain also slightly augmented NK cell activity, but were less effective than EPS itself. The EPS-dependent stimulation of NK cell activity was abrogated in IFN-γ knockout mice and in myeloid differentiation factor 88 knockout mice. Furthermore, IFN-γ production from spleen cells stimulated with EPS was completely blocked with both anti-IL-12 and anti-IL-18 antibodies in vitro. These findings suggest that NK cell activation by OLL1073R-1 yogurt is EPS-dependent, occurs via IL-12- and IL-18-mediated IFN-γ production, and requires myeloid differentiation factor 88. We showed that traditional Bulgarian yogurt could exert immunostimulatory effects by selecting starter strains and part of the mechanisms depend on IFN-γ inducible EPS produced from L. delbrueckii ssp. bulgaricus. Further investigations on processes of fermentation to increase of the EPS may lead to the development of new functional foods that keep our immune functions stable.

Characterization and in vitro immunomodulatory screening of fructo-oligosaccharides of Asparagus racemosus Willd.

Asparagus racemosus Linn. (Fam. Liliaceae) is an ethno-pharmacologically acclaimed Ayurvedic medicinal plant. In the present study, aqueous extract of A. racemosus (ARC) was fractionated and screened for the polysaccharide fraction (ARP). The characterization was done by enzymatic, Size Exclusion, gas chromatography with flame ionization detector (GC–FID), high pressure anion exchange chromatography (HPAEC) and thin layer chromatographic analyses. Phyto-chemical evaluation confirmed the presence of 26.7% of 2→1 linked fructo-oligosaccharides (FOS). They have a degree of polymerization (DP) of nearly 7–8. Cytotoxicity evaluation on P388 cell lines was consistent with low cytotoxicity of the extracts. In vitro Natural Killer (NK) cell activity was evaluated using human peripheral blood mononuclear cells (PBMC) isolated from whole blood on a ficoll-hypaque density gradient. K562 a myeloid leukemia cell line, were used as target cells. ARC, tested over the range 0.2–50μg/ml, showed a dose-related stimulation of NK cell activity with a peak increase of 16.9±4.4% at 5.6μg/ml. However, ARP demonstrated a higher stimulatory activity of 51.8±1.2% at 25μg/ml. The results indicate that the FOS from A. racemosus potentiates the NK cell activity and this could be an important mechanism underpinning the ‘Rasayana’ properties of this plant.

Stimulating natural killer cells to protect against cancer: recent developments

Current cancer immunotherapies have begun to target cell types involved in innate immunity, such as natural killer (NK) cells that recognize and kill tumor cells. Recent advances in the study of NK cell biology have generated interest in manipulating these cells to generate anti-tumor responses. A rise in the number of activated NK cells has been shown to prevent and treat cancer in many preclinical models and is a positive clinical factor in human tumors. This article will focus on recent research on the ability of IL-15 and Toll-like receptor ligands to stimulate NK cell activity against cancer. The potential of these therapies, both alone and in conjunction with traditional and other vaccine platforms, will be reviewed. The current status of these therapies in clinical trials will also be discussed. Targeting these cell types in the context of human cancers may be an essential factor in future cancer treatments.

Immunomodulatory Polysaccharide from Chlorophytum borivilianum Roots

Chlorophytum borivilianum Santapau & Fernandes (Liliaceae) is an ayurvedic Rasayana herb with immunostimulating properties. The polysaccharide fraction (CBP) derived from hot water extraction of C. borivilianum (CB), comprising of ∼31% inulin-type fructans and ∼25% acetylated mannans (of hot water-soluble extract), was evaluated for its effect on natural killer (NK) cell activity (in vitro). Human peripheral blood mononuclear cells (PBMCs), isolated from whole blood on a Ficoll-Hypaque density gradient, were tested in the presence or absence of varying concentrations of each C. borivilianum fraction for modulation of NK cell cytotoxic activity toward K562 cells. Preliminary cytotoxicity evaluation against P388 cells was performed to establish non-cytotoxic concentrations of the different fractions. Testing showed the observed significant stimulation of NK cell activity to be due to the CBP of C. borivilianum. Furthermore, in vivo evaluation carried out on Wistar strain albino rats for humoral response to sheep red blood cells (SRBCs) and immunoglobulin-level determination using enzyme-linked immunosorbent assay (ELISA), exhibited an effectiveness of C. borivilianum aqueous extract in improving immune function. Present results provide useful information for understanding the role of CBP in modulating immune function.

Natural killer cells and malaria

Malaria, caused by the infection with parasites of the germs Plasmodium, is one of the three most important infectious diseases worldwide, along with tuberculosis and infection with human immunodeficiency virus. Natural killer (NK) cells are lymphocytes classically involved in the early defense against viral infections and intracytoplasmic bacterial infections and are also implicated during the course of tumor development and allogeneic transplantation. These cells display important cytotoxic activity and produce high levels of proinflammatory cytokines. In both mouse and human models of malaria, NK cells appear to be a major source of interferon-gamma during the early phase of infection. In humans, indirect signaling through monocytes/macrophages required to optimally stimulate NK cell activity. However, the in vivo functions of NK cells during malaria are still enigmatic, and many issues remain to be dissected, such as the molecular basis of the direct recognition of iRBCs by NK cells.

Effects of growth hormone and insulin-like growth factor I binding to natural killer cells.

Human growth hormone (GH) and insulin-like growth factor I (IGF-I) are known to bind to, and exert modulatory effects on, different immunocompetent cells, including CD16+/CD3- natural killer (NK) cells. NK cells are involved in various non-major-histocompatibility-complex-restricted actions of the immune system. Although no clinically significant defect in tumour or virus defence has been reported in GH-deficient patients, the data available indicate decreased NK cell activity in these patients. In most studies, the absolute number and percentage of NK cells have been found to be normal. Substitution with GH has been reported to normalize the decreased NK cell activity in GH-deficient patients. In a cross-sectional study in GH-deficient adults, decreased basal and interferon-beta (IFN-beta)-stimulated NK cell activity in vitro. Preliminary data on GH binding to NK cells indicate enhanced binding in GH-deficient patients when compared with normal controls.

The Effects of General Anesthesia and Surgery on Basal and Interferon Stimulated Natural Killer Cell Activity of Humans

Natural killer (NK) cells can lyse certain tumor cells as well as virally infected cells without prior sensitization.Animal studies have shown that general anesthesia (GA) alone or GA followed by surgery decreases both basal NK cytotoxicity and enhancement of NK activity by interferon (IFN). The purpose of this study was to determine whether similar inhibition of NK activity by anesthesia and surgery occurs in humans. Venous blood was drawn 1 h before and 20-24 h after surgery under isoflurane/N2 O anesthesia. Peripheral blood mononuclear cells (PBMC) were assayed for basal and IFN-alpha-stimulated NK cytotoxicity using a chromium release assay with K562 cells as targets. Flow cytometry was used to enumerate NK, T-helper, and T-cytotoxic/suppressor cell populations in each sample. Basal NK activity was significantly depressed after GA and GA and surgery. Although the postoperative IFN treatment increased NK activity to the preoperative basal level, the level achieved was significantly lower than the level observed after IFN stimulation of PBMC as evaluated preoperatively. This decreased activity does not seem to be the result of a decrease in the percentage of circulating NK cells. The decrease in NK activity after anesthesia and surgery may lead to increased susceptibility to infection and/or tumor dissemination and thus needs to be explored. Implications: Natural killer cells can kill cancer cells and virally infected cells. This study shows that surgery with general anesthesia leads to decreased natural killer cell activity as assessed in the laboratory. This decreased natural killer cell activity may lead to infection or tumor dissemination. NK activity can be restored to presurgery levels by treating isolated NK cells with interferon-alpha. (Anesth Analg 1997;85:918-23)

The Effects of General Anesthesia and Surgery on Basal and Interferon Stimulated Natural Killer Cell Activity of Humans

Natural killer (NK) cells can lyse certain tumor cells as well as virally infected cells without prior sensitization. Animal studies have shown that general anesthesia (GA) alone or GA followed by surgery decreases both basal NK cytotoxicity and enhancement of NK activity by interferon (IFN). The purpose of this study was to determine whether similar inhibition of NK activity by anesthesia and surgery occurs in humans. Venous blood was drawn 1 h before and 20-24 h after surgery under isoflurane/N2O anesthesia. Peripheral blood mononuclear cells (PBMC) were assayed for basal and IFN-alpha-stimulated NK cytotoxicity using a chromium release assay with K562 cells as targets. Flow cytometry was used to enumerate NK, T-helper, and T-cytotoxic/suppressor cell populations in each sample. Basal NK activity was significantly depressed after GA and GA and surgery. Although the postoperative IFN treatment increased NK activity to the preoperative basal level, the level achieved was significantly lower than the level observed after IFN stimulation of PBMC as evaluated preoperatively. This decreased activity does not seem to be the result of a decrease in the percentage of circulating NK cells. The decrease in NK activity after anesthesia and surgery may lead to increased susceptibility to infection and/or tumor dissemination and thus needs to be explored. Natural killer cells can kill cancer cells and virally infected cells. This study shows that surgery with general anesthesia leads to decreased natural killer cell activity as assessed int he laboratory. This decreased natural killer cell activity may lead to infection or tumor dissemination. NK activity can be restored to presurgery levels by treating isolated NK cells with interferon-alpha.

Insulin-like growth factor I is an independent coregulatory modulator of natural killer (NK) cell activity.

We aimed to investigate the natural killer (NK) cell activity in hGH-deficient adults and to analyze the effect of insulin-like growth factor (IGF)-I in vivo and in vitro on NK cell activity. NK cell activity was measured in a 4-h nonisotopic assay with europium-labeled and cryopreserved K-562 cells. NK-cell numbers were measured after incubation with murine monoclonal CD3 and CD16 antibodies by flow cytometry analysis. In a cross-sectional study, the basal and interferon-beta (IFN-beta) stimulated (1000 IU/ml) NK cell activity of 15 hGH-deficient patients and 15 age- and sex-matched controls was measured. The percentages and absolute numbers of CD3-/16+ NK-cells were not significantly different in the patient vs. control group. The basal and IFN-beta stimulated NK cell activity however was significantly decreased in the patient vs. control group at all effector/target (E/T) cell ratios from 12.5-100 (e.g. 17 +/- 3 vs. 28 +/- 3% lysis without IFN-beta, P < 0.05, and 42 +/- 4 vs. 57 +/- 4% lysis with IFN-beta, P < 0.05; both at E/T 50). IGF-I levels of patients and controls showed a significant positive correlation with NK cell activity (r = 0.37; P < 0.05). In an IGF-I in vitro study (IGF-I in vitro 250-1250 microg/L), the basal and IFN-beta stimulated NK cell activity of 13 hGH-deficient patients and of 18 normal subjects was significantly enhanced by IGF-I in vitro (e.g. GH-deficient patients: 9 +/- 2 vs. 10 +/- 2% lysis without IFN-beta, P < 0.05 and 25 +/- 4 vs. 30 +/- 4% lysis with IFN-beta, P < 0.005; and normal subjects: 15 +/- 3 vs. 23 +/- 3% lysis without IFN-beta, P < 0.001 and 35 +/- 4 vs. 44 +/- 5% lysis with IFN-beta, P < 0.001; both at IGF-I 500 microg/L). In summary, in our cross-sectional study, adult GH-deficient patients showed a significantly lower basal and IFN-beta stimulated NK cell activity than matched controls, despite equal NK cell numbers. IGF-I levels of patients and controls showed a weak positive correlation with NK cell activity. In an in vitro study, IGF-I significantly enhanced basal and IFN-beta stimulated NK cell activity of hGH-deficient patients and also of normal subjects. The decreased NK cell activity in GH-deficient patients may be caused at least in part by low serum IGF-I levels. IGF-I appears to be an independent coregulatory modulator of NK cell activity.

Comparison of the in vivo effects of morphine and methadone on natural killer cell activity in spleen, peritoneal cavity, and lungs in rats

Opiates and opioid agents are known to affect the immune system. In humans this includes alterations in natural killer (NK) cell activity. Morphine is reported to reduce in vivo spleen NK activity in rats, whereas for methadone only in vitro data have been described. In the present paper we describe a systematic study on the chronic effects of well-known opiates, comparing for the first, time the effects of morphine and methadone on NK cell activity in various organs: in addition to spleen, also in the peritoneal cavity, and lungs. In all organs the NK activity was determined using three effector: target cell ratios. Morphine and methadone given by food during 6 weeks decreased the NK cell activity in rat spleen, supporting published data on morphine. The role of the opiate receptor is discussed. However, the overall action of morphine could not be described as suppressive because stimulation of NK cell activity in the peritoneal cavity and lungs by morphine was found. In contrast, methadone induced a decrease in the NK cell activity in these organs. Apart from these differential expressions of morphine-and methadone associated effects on NK cell activity, the findings demonstrate the potential adverse effects of these opiates on an important antiviral defence mechanism.

Expression of the conditioned NK cell activity is β-endorphin dependent

We are interested in identifying the pathways which are responsible for triggering the conditioned enhancement of natural killer (NK) cell activity. Earlier studies have suggested that central opioid(s) are involved in eliciting the expression of the conditioned NK cell activity. The purpose of this study was to identify the central opioid peptides that allow the central nervous system (CNS) to communicate with the immune system. Mediators that activate the efferent pathway of communication between the CNS and immune system was examined by injection of the mediator via the cisterna magna (CM). Conditioning was used as a tool to show that the bi-directional communication between the CNS and the immune system does take place. We found that β-endorphin but not dynorphin could stimulate NK cell activity, when β-endorphin or dynorphin was injected into the CM. In addition, when anti-β-endorphin or anti-dynorphin antibody was injected into the conditioned animals via CM the conditioned response was blocked by anti-β-endorphin but not by anti-dynorphin antibody. These observations suggest that β-endorphin appears to be one of the signals that is induced in the brain at the CS recall step of the conditioned response to trigger the elevation of NK cell activity.

Contribution of plasma cortisol to corticosteroid-suppressed peripheral blood natural killer cell activity in Crohn's disease

We recently showed that patients with active ileocecal Crohn's disease (CD) have a temporarily suppressed peripheral blood natural killer (NK) cell activity during treatment with oral budesonide or prednisolone. This suppression was caused by a decrease in the number of CD16+ NK cells in the circulation. In the present study we evaluated the contribution of cortisol in plasma to this suppressed NK cell activity. The CD patients took part in a controlled study where they received either oral budesonide or prednisolone for 10 weeks. Before treatment, and at 4 and 10 weeks of treatment, peripheral blood NK cell activity, numbers of circulating CD 16+ NK cells, and plasma cortisol levels were analysed. These parameters were determined both before and 30 min after administration of adrenocorticotropic hormone (ACTH). The ACTH-induced plasma cortisol increase was accompanied by a stimulated NK cell activity, when both are suppressed by corticosteroid treatment, without changing the number of CD16+ NK cells. Therefore, a low plasma cortisol level contributes to the corticosteroid mediated NK cell suppression in active ileocecal CD.

Natural killer cell activity in long-term survivors of testicular cancer. Influence of cytostatic therapy and initial stage of disease.

Patients with testicular cancer can be cured by cisplatin-based chemotherapy in many cases. Thus, concern about possible late toxicities of treatment is warranted. In this investigation, the absolute number of natural killer (NK) cells according to their CD56+ phenotype, NK cell activity, and antibody dependent cellular cytotoxicity (ADCC) were investigated in 29 patients with seminomas or nonseminomatous germ cell tumors (NSGCT) a median of 31 months (range, 5-73 months) after termination of chemotherapeutic treatment. No difference in the absolute number of NK cells, NK cell activity, and ADCC was found between patients with testicular cancer after either standard polychemotherapy consisting of bleomycin, etoposide, and cisplatin (BEP) or monotherapy with carboplatin and healthy control subjects. When patients were analyzed further using multivariate analysis, a significant (P < 0.05) detrimental influence of BEP polychemotherapy versus carboplatin monotherapy on NK cell activity was found. Moreover, NK cell activity also depended significantly (P < 0.05) on the time elapsed after chemotherapy was administered, but normalized with time. Because the absolute number of NK cells was not affected, is was assumed that polychemotherapy induced a functional defect. In a subanalysis of patients with NSGCTs, metastases at diagnosis resulted in a significant (p < 0.05) and persistent stimulation of NK cell activity but not of ADCC. Cytostatic chemotherapy in patients with testicular cancer did not lead to compromised lytic effector cell function as assessed by NK cell activity and ADCC. However, a short, time-dependent reduction was found that also depended on the intensity of chemotherapeutic treatment. This finding related to the observation of a long-lasting stimulus of NK cell activity by initial metastases in patients with NSGCTs.

Effect of diet and plasma fatty acid composition on immune status in elderly men

The relationship between fatty acids in plasma and basal (B), interleukin-2-(IL-2), and interferon-alpha (IFN-alpha)-stimulated natural killer (NK) cell activity was studied in healthy elderly men aged on average 70.5 y (65-81 y). B-NK correlated significantly with the fraction of plasma fatty acids consisting of total polyunsaturated fatty acids (PUFAs), total n-6 fatty acids, and linoleic acid (r = -0.68, r = -0.62, and r = -0.52, respectively). Significant negative correlations were also found between IFN-alpha stimulated NK cells and the three groups of fatty acids and between IL-2-stimulated NK cells and PUFAs. Likewise, negative correlations between PUFAs in the diet and B-NK, IL-2 and IFN-alpha stimulated NK cell activity were found. The number of NK cells increased significantly but NK cell activity did not change after 5 wk on a diet lower in fat but higher in PUFAs than the subjects' habitual diet. It is concluded that the amount and type of dietary fatty acids influence in vitro measures of immune function in elderly men. From an immunological point of view, a high intake of n-6 PUFAs may be inadvisable.

Effect of dexamethasone on conditioned enhancement of natural killer cell activity.

It is believed that the expression of the conditioned natural killer cell activity is regulated through the hypothalamus-pituitary axis. Since the conditioned expression of both the plasma level of adrenocorticotropic hormone and natural killer (NK) cell activity show a sequential rise after exposure to the conditioned stimulus, it was of interest to determine if treatment with dexamethasone could inhibit this response. These studies suggest that treatment with dexamethasone was able to block the expression of the conditioned NK cell activity but was unable to interfere with the pairing of the conditioned stimulus with the unconditioned stimulus. We conclude that the hypothalamic pituitary axis is an integral part of the pathway for stimulation of NK cell activity in the spleen.

Contact of lymphocytes with Helicobacter pylori augments natural killer cell activity and induces production of gamma interferon.

We studied the capacity of glutaraldehyde-fixed Helicobacter pylori to stimulate natural killer (NK) cell activity. Bacteria were incubated overnight with peripheral blood lymphocytes enriched for large granular lymphocytes (LGL), the mediators of non-major histocompatibility complex-restricted cellular cytotoxicity. Then, the cytolytic activity of LGL was tested against various tumor target cells. We observed that efficient cytolytic activity was generated against resistant and nonresistant tumor target cell lines. Nine local clinical isolates of H. pylori and the reference strain NCTC 11637 were tested, and they all were equally effective in inducing NK cell activity. However, flagellin antigen, glycine extract, urease, and lipopolysaccharide prepared from H. pylori NCTC 11637 all failed to induce significant NK cell activity. The supernatants which were collected after coincubation of bacteria with LGL contained a factor(s) which could activate resting LGL into efficient cytolytic activity. The supernatants were also analyzed for interferon (IFN) activity. We observed that high titers of IFN were produced and that IFN activity was neutralized with anti-gamma interferon (IFN-gamma) antiserum, but not with anti-IFN-alpha antiserum. Thus, contact of lymphocytes with H. pylori leads to efficient stimulation of NK cell activity and the production of IFN-gamma.