Low Natural Killer Activity Research Articles

Effect of Heat-Treated Lactiplantibacillus plantarum nF1 on the Immune System Including Natural Killer Cell Activity: A Randomized, Placebo-Controlled, Double-Blind Study.

Heat-treated Lactiplantibacillus plantarum nF1 (HT-nF1) increases immune cell activation and the production of various immunomodulators (e.g., interleukin (IL)-12) as well as immunoglobulin (Ig) G, which plays an important role in humoral immunity, and IgA, which activates mucosal immunity. To determine the effect of HT-nF1 intake on improving immune function, a randomized, double-blind, placebo-controlled study was conducted on 100 subjects with normal white blood cell counts. The HT-nF1 group was administered capsules containing 5 × 1011 cells of HT-nF1 once a day for 8 weeks. After 8 weeks of HT-nF1 intake, significant changes in IL-12 were observed in the HT-nF1 group (p = 0.045). In particular, the change in natural killer (NK) cell activity significantly increased in subjects with low secretory (s) IgA (≤49.61 μg/mL) and low NK activity (E:T = 10:1) (≤3.59%). These results suggest that HT-nF1 has no safety issues and improves the innate immune function by regulating T helper (Th)1-related immune factors. Therefore, we confirmed that HT-nF1 not only has a positive effect on regulating the body's immunity, but it is also a safe material for the human body, which confirms its potential as a functional health food ingredient.

Blood natural killer cells during treatment in recurrent ovarian cancer

Objective Recent research indicated favorable prognostic impact of intratumoral natural killer (NK) cells in ovarian carcinoma (OC). The role of NK cells during chemotherapy in OC is unknown. We investigated impact of NK cells in OC patients treated with palliative chemotherapy. Methods Participants receiving palliative chemotherapy for recurrent OC (N = 72) had prospectively blood samples at baseline and before cycle 2. NK cell counts were quantified by flow cytometry. NK cell activity was measured by the NK Vue® assay, estimating interferon-gamma production. Overall survival (OS) was the primary endpoint. Cutoffs were predefined, NK numbers (≥184 × 106 cells/L vs. <184 × 106 cells/L) and NK activity (<200 pg/mL vs. ≥200 pg/mL). Results Median OS in patients with low vs. high NK cell count at baseline was 7.1 months vs. 15.6 months (p = .028), respectively, and before cycle 2 was 5.7 vs. 17.3 months, p < .001, respectively. The difference in restricted mean survival (ΔRMST) was 5.7 months (95% CI: 3.3–8.0) at cycle 2 vs. 2.5 months (95% CI: −0.6 to 5.6) at baseline, showing a significant difference with no overlap of confidence intervals. In multivariate analyses, low NK cell count remained significant with a hazard ratio (HR)=2.83, 95% CI: 1.53–5.22, p = .001 (baseline) and HR = 3.34, 95% CI: 1.67–6.71, p = .001 (before cycle 2). Patients with both low NK count and NK activity at baseline (N = 20) had median OS 6.5 months vs. 11.5 months in patients with either high activity, high count or both (p = .007). In parallel, patients with both low NK activity and count at cycle 2 (N = 18) had a median survival of 4.0 months vs. 15.4 months (p < .001). Conclusions A low blood NK cell count in recurrent metastatic ovarian cancer during chemotherapy is associated with unfavorable prognostic impact. Early increase in survival difference based on NK cell status suggests an association between NK cell count and treatment benefit.

Apoptotic Potential of Secretome from Interleukin-Induced Natural Killer Cells toward Breast Cancer Cell Line by Transwell Assay

Breast cancer (BC) is the number one cause of deaths from cancer in women. Metastasis in BC is caused by immunosurveillance deficiency, including impairment of Natural Killer (NK) cell maturation, low NK activity, and decreasing cytotoxicity. This study was performed to improve activating receptors and cytotoxicity of NK cells using interleukin 15 (IL15) against BC cells. Human recombinant IL15 was used to induce NK cells. To evaluate the potential of IL15 in inducing NK cells, we measured the activating and inhibiting receptors (NKG2D, NKG2A), apoptotic potency of NK cells on BC cells (MCF7) using transwell assay. The IL15 inducer on the NK cell were measured NKG2D, NKG2A gene expression with quantitative polymerase chain reaction (qPCR), (GzmB) secretion using ELISA, apoptotic gene expression of MCF7 using qPCR. IL15 increased NKG2D expression 4.01-9.13%, but IL15 could not affect toward NKG2A expression on NK cells. IL15-activated NK cells, inhibited BC cells proliferation, induced apoptotic BC cells 25.89-32.19%, induced apoptotic genes of BC cells bax, p53. IL15 increase NK activating receptor (NKG2D), inhibit BC cells proliferation, induce apoptotic percentage and induce apoptotic gene expression.

Delay of Regulatory T Cell Reconstitution in Elderly Patients Increases the Frequency of Chronic Graft-Versus-Host Disease after Allogeneic Hematopoietic Stem Cell Transplantation

Background: Regulatory T cells (Treg) play important roles in onset of graft-versus-host disease (GVHD) and chronic GVHD (cGVHD) in elderly people is more frequent than in younger people after allogeneic hematopoietic stem cell transplantation (HCT). However, little is known about the differences in the number and function of Treg and natural killer (NK) cells in elderly and young patients. In this study, we examined the cause of the difference in incidences of cGVHD in these patient populations by measuring Treg and NK cells over time after HCT. Patients and Methods: The subjects were 65 consecutive patients aged &gt;18 years who underwent HCT for different hematologic diseases at our hospital between December 2008 and December 2018 and survived for &gt;100 days after HCT. The median age was 57 years (range: 19-73 years), and those aged ≥58 (n=33) and ≤57 (n=32) were classified as elderly and younger patients, respectively. Evaluated variables included recipient and donor characteristics, and transplant-related factors, including conditioning regimen, donor type, degree of match, and GVHD prophylaxis. After obtaining informed consent, blood was drawn from all patients on day 100 and at 12-month intervals thereafter. Analysis of CD4+CD25+Foxp3+ Treg cells, CD3+CD4+ T cells, CD3+CD8+ T cells, CD19+ B cells, and CD3-CD56+ NK cells was performed using flow cytometry, and the absolute numbers of these cells were calculated. NK activity was measured by the standard 51Cr release assay at an effector:target (E:T) ratio of 20:1. Results: The incidence of grades II-IV acute GVHD was 29.2% at 100 days. There was no difference in the incidence of acute GVHD between elderly and younger patients [HR=0.85, 95% CI 0.34-2.09, p=0.72]. However, the overall incidence of cGVHD was 37.1%. In univariate analysis, the incidence of cGVHD in elderly patients was significantly higher than that in younger patients [HR=3.61, 95% CI 1.13-11.59, p=0.031]. Elderly patients had a significantly lower percentage of B cells than younger patients at 24 months (13.4±9.6% vs. 27.0±15.6%, p=0.024) and 36 months (16.4±10.3% vs. 31.1±11.2%, p&lt;0.01); and also had a lower percentage and absolute number of Treg cells at 12 months (0.24±0.10% vs. 0.47±0.32%, p=0.010; 14.8±7.7 /µl vs. 24.0±18.4 /µl, p=0.061) and 36 months (0.17±0.15% vs. 0.37±0.20%, p&lt;0.01; 12.7±8.54 /µl vs. 20.9±12.9 /µl, p=0.046). The percentage and absolute number of CD8+ cells were higher in elderly patients at 12 months (50.4±17.2% vs. 33.5±12.9%, p&lt;0.01; 1130.5±588.5 /µl vs. 611.8±365.9 /µl, p=0.016) and 24 months (46.2±10.8% vs. 26.1±9.7%, p&lt;0.01; 1115.7±484.2 /µl vs. 584.2±372.2 /µl, p&lt;0.01). However, elderly patients had a lower percentage of NK cells at 12 months (11.9±8.0% vs. 20.1±14.5%, p=0.045) and lower NK activity at 24 months (24.0±14.0% vs. 47.6±16.3%, p&lt;0.01). The same results were obtained in 50 cases after exclusion of patients who developed cGVHD (≥58, n=22; ≤57, n=28). Thus, the 22 elderly patients had a lower percentage and absolute number of Treg cells at 12 months (0.22±0.16% vs. 0.47±0.32%, p=0.015; 14.1±8.3 /µl vs. 24.0±18.4 /µl, p=0.071) and 36 months (0.16±0.11% vs. 0.40±0.20%, p&lt;0.01; 12.2±9.2 /µl vs. 22.7±12.7 /µl, p=0.023), and a higher percentage and absolute number of CD8+ cells at 12 months (49.0±18.8% vs. 33.5±12.9%, p=0.031; 1181.9±619.0 /µl vs. 611.8±365.9 /µl, p=0.015) and 24 months (45.6±11.4% vs. 25.4±9.6%, p&lt;0.01; 1067.6±494.1 /µl vs. 587.1±382.9 /µl, p=0.012). Conclusion: The percentage and absolute number of Treg cells in elderly patients were significantly lower than those in younger patients, whereas CD8+ T cells were significantly higher in elderly patients after HCT. The absolute number of Treg cells tended to reconstitute one year after HCT in younger patients, but tended to decrease gradually in elderly patients, with no recovery even three years after HCT. In contrast, there was no change in NK cells. Similar results were obtained in an analysis excluding patients who developed cGVHD. These results suggest that a difference in immunological reconstitution between elderly and younger patients may explain the difference in the incidence of cGVHD between these patients. This may be useful in determining the choice of therapy with consideration of the immunologic mechanism. Disclosures Suzumiya: Celgene, Kyowa Kirin, Chugai-Roche, Eisai, Takeda, Celltrion, SymBio, Astellas, Ono, AstraZeneca, Ootsuka, Taiho, Mundi, Dainihon-Sumitomo: Research Funding.

Oxidative stress and immunosenescence in spleen of obese mice can be reversed by 2-hydroxyoleic acid.

What is the central question of this study? Evidence is growing for the link between obesity, immune dysfunction and oxidative stress, but it is still not known how the properties and functions of the spleen and splenic leucocytes are affected. What is the main finding and its importance? Obesity led to premature immunosenescence, manifested as oxidative stress and changes in leucocyte functions in mouse spleen. The oleic acid derivative 2-hydroxyoleate and, to a lesser extent, a combination of eicosapentaenoic and docosahexaenoic acids could reverse most of the observed alterations, suggesting a potential therapeutic tool for obesity-related immune dysfunction and redox imbalance. We aimed to investigate the effects of obesity on oxidative stress and leucocyte function in the mouse spleen and to assess whether supplementation with 2-hydroxyoleic acid (2-OHOA) or n-3 polyunsaturated fatty acids (PUFAs) could reverse those effects. Female ICR/CD1 mice (8weeks old, n=24) received an obesogenic diet (22% fat for 4weeks and 60% fat for 14weeks). After 6weeks, mice were divided into the following three groups (n=8 per group): no supplementation; 2-OHOA supplementation (1500mgkg-1 of diet); and n-3 PUFA supplementation (eicosapentaenoic acid and docosahexaenoic acid, 1500+1500mgkg-1 of diet). Eight mice were fed the standard diet for the whole duration of the study (control group). At the end of the experiment, the following variables were assessed in spleens: levels of reduced (GSH) and oxidized glutathione (GSSG), GSH/GSSG, xanthine oxidase activity, lipid peroxidation, lymphocyte chemotaxis, natural killer activity and mitogen (concanavalinA and lipopolysaccharide)-induced lymphocyte proliferation. Obese animals presented higher GSSG levels (P=0.003), GSSG/GSH ratio (P=0.013), lipid peroxidation (P=0.004), xanthine oxidase activity (P=0.015) and lymphocyte chemotaxis (P<0.001), and lower natural killer activity (P=0.003) and proliferation in response to concanavalinA (P<0.001) than control mice. 2-Hydroxyoleic acid totally or partly reversed most of the changes (body weight, fat content, GSSG levels, GSH/GSSG, lipid peroxidation, chemotaxis and proliferation, all P<0.05), whereas n-3 PUFAs reversed the increase in xanthine oxidase activity (P=0.032). In conclusion, 2-OHOA or, to a lesser extent, n-3 PUFAs could ameliorate the oxidative stress and alteration of leucocyte function in the spleens of obese mice. Our findings support a link between obesity and immunosenescence and suggest a potential therapeutic tool for obesity-related immune dysfunction.

A significantly impaired natural killer cell activity due to a low activity on a per-cell basis in rheumatoid arthritis

To elucidate the characterization of peripheral natural killer (NK) cells in patients with rheumatoid arthritis (RA), we investigated the NK cell activity, the expression of NK cell activating receptors and intracellular molecules. The NK activity was analyzed in 27 RA patients, 22 primary Sjögren’s syndrome (SS) patients, and 15 healthy individuals using the 51Chrominium release assay. The expression of NK cell activating receptors (NKG2D, CD244, CD2, and CD16) and intracellular molecules (granzyme B, perforin, and TCR ζ chain) in CD3-CD56+ cells were characterized by flow cytometry. The serum cytokine levels (IL-6, TNFα, and IL-18) were measured using ELISA. Both the NK cell activity and the activity on a per-cell basis were observed to significantly decrease in the RA patients in comparison to the controls. The expression of NKG2D and CD244 also significantly decreased in both the RA and primary SS patients, whereas the significant decrease in the CD16 expression was only observed in the RA patients. The titer of the serum IL-6, TNFα, and IL-18 was significantly higher in the RA patients than in the controls. These data suggest that a low NK activity on a per-cell basis might therefore contribute to an impaired NK activity in the patients with RA.

A significantly impaired natural killer cell activity due to a low activity on a per-cell basis in rheumatoid arthritis

To elucidate the characterization of peripheral natural killer (NK) cells in patients with rheumatoid arthritis (RA), we investigated the NK cell activity, the expression of NK cell activating receptors and intracellular molecules. The NK activity was analyzed in 27 RA patients, 22 primary Sjögren's syndrome (SS) patients, and 15 healthy individuals using the (51)Chrominium release assay. The expression of NK cell activating receptors (NKG2D, CD244, CD2, and CD16) and intracellular molecules (granzyme B, perforin, and TCR zeta chain) in CD3-CD56+ cells were characterized by flow cytometry. The serum cytokine levels (IL-6, TNFalpha, and IL-18) were measured using ELISA. Both the NK cell activity and the activity on a per-cell basis were observed to significantly decrease in the RA patients in comparison to the controls. The expression of NKG2D and CD244 also significantly decreased in both the RA and primary SS patients, whereas the significant decrease in the CD16 expression was only observed in the RA patients. The titer of the serum IL-6, TNFalpha, and IL-18 was significantly higher in the RA patients than in the controls. These data suggest that a low NK activity on a per-cell basis might therefore contribute to an impaired NK activity in the patients with RA.

Correlation Between Defective NK Activity and Low Expression of CD16, NKp44 and NKG2D in Beta Thalassemia Patients

Beta thalassemia patients have a major global impact on health and mortality and are characterized by absence of beta globin chain production. In most patients, multiple blood transfusions can induce differences of immune response Therefore, they are often associated with bone marrow expansion and immunodeficiency in terms of lymphocyte subsets and cytokine levels in the peripheral blood and presence of alloantibodies. We have previously shown that children with beta thalassemia major have had decreased NK cells. Natural killer (NK) cells are lymphocyte subpopulations that are important effectors of innate immune responses against infectious pathogens and tumor cells. The cytotoxic activity of NK cells is regulated by the equilibrium between positive and negative signals from multiple receptors expressed on their cell surface; signals that can trigger the cytolytic machinery as well as cytokine or chemokine secretion. The activator receptors of NK cells are natural cytotoxicity receptors (NCR) and NKG2D. NCR are represented by NKp46, NKp44, and NKp30. These receptors, upon engagement by their specific ligands, induce a strong activation of NK-mediated cytotoxic activity. NKp44, a triggering receptor selectively expressed by activated NK cells. NK cells can make cytolytic function by regulating pro-inflammatory cytokines as IFN-gamma, TNF-alpha and IL10. This study was carried out to investigate details NK cell function of 27 transfusion-dependent children with beta thalassemia. Data from 18 age- and sex-balanced children served as controls. For this purpose, we analyzed their cytolytic function against K562 cells in both pure NK cells (CD56+CD16+CD3−) and PBMC. Before and after the assessment of NK activity, we have examined the levels of NK activating receptors expressed on NK cells. The expression levels of the activation receptors (NKp30, NKp44, NKG2D) on CD56+CD16+CD3− NK cells was quantified by multicolour immunofluorescent analysis using flow cytometry. In addition, supernatant IL2, IL12, IFN-gamma, TNF-alpha, TFG-beta, IL10 levels after induced K562 cells were measured by ELISA. We observed that beta thalassemia patients had lower NK activity than controls. Before the assessment of NK activity, we found that NKG2D (2064.03+/−638.64/molecule, p<0.04) and NKp44 (1057.03+/−211.21/molecule, p<0.01) surface density was reduced in a statistically significant manner in beta thalassemia patients. This phenotype correlated with low cytolytic activity. No statistically significant differences were found in the expression of NKp30. In our experimental setting where NK cells encountered K562 targets, samples from patients had significantly increased TGF-beta (544.25+/−521.5 pg/ml, p<0.03), IL10 (16.14+/−11.1 pg/ml p<0.04) when compared with controls. In addition, expression of CD16 of NK cells that induced against K562 only (12924.47+/−6913.37/molecule, p<0.006) significantly increased in controls. As a result, our findings demonstrate that environmental factors such as ineffective cytokine production and functionally defective monocytes, may cause low NK activity in beta thalassemia patients.

Decreased risk of colorectal cancer with the high natural killer cell activity NKG2D genotype in Japanese

NKG2D is an immune receptor on natural killer (NK) and other cells active in the immune system. It recognizes ligands expressed on mainly transformed cells and plays a role in their elimination through the so-called 'cancer immune surveillance'. It was reported that there are two haplotypes of NKG2D, HNK1 (high NK activity) and LNK1 (low NK activity). Harboring the HNK1 is reported to reduce the overall cancer risk. To elucidate its impact on colorectal cancer (CRC), we conducted the present case-control study. The subjects were 379 CRC patients and 1137 sex-age-matched non-cancer controls. Data on lifestyle factors including diet were obtained by self-administered questionnaire. The NKG2D genotypes (rs1049174: G-C, LNK1/LNK1:CC; LNK1/HNK1:CG and HNK1/HNK1:GG) were assessed by the TaqMan method. Associations were then assessed by multivariate logistic regression models, considering potential confounders. The measure of association was the odds ratio (OR) and its confidence intervals (CIs). We found a reduced risk of CRC with the NKG2D HNK1. Adjusted ORs were 0.77 for LNK1/HNK1 (95% CI: 0.60-0.99) and 0.48 for HNK1/HNK1 (0.32-0.72) relative to LNK1/LNK1. The same association was consistently observed with stratified analyses across all confounders except regular exercise and body mass index (BMI). Thus, the impact of harboring HNK1 was more evident among those with BMI >/= 25 and those exercising regularly, suggesting possible interactions between NKG2D genotype and these factors. We found that the HNK1 genotype, associated with high NK cell activity, might be an independent protective factor for CRC among the Japanese population. This possibility warrants further analysis.

Preferential apoptosis of CD56dim natural killer cell subset in patients with cancer.

Natural killer (NK) cells (CD56(+)/CD3(-)) in the circulation of cancer patients were reported to have low NK activity and undergo spontaneous apoptosis. A possible relationship between apoptosis and impaired NK activity was studied by Annexin V-binding and NK-cell assays performed with peripheral blood mononuclear cells of patients with head and neck cancer (HNC), breast cancer (BC) and normal controls (NC). Cells stained with Annexin V (Anx) and antibodies to CD56, CD3, CD95, CD25, CD122 or CD132 were examined by flow cytometry. NK activity was tested against K562 targets in 4-h (51)Cr-release assays. The ratio of CD56(dim)/CD56(bright) NK cells was significantly different in patients vs. controls (10 vs. 16; p<0.01). A significantly greater percentage of CD56(dim) NK cells bound Anx in HNC patients (27+/-17%, median +/- SD) or BC (46+/-18%) than in NC (15+/-18%, p<0.04 and p<0.0002, respectively). CD56(dim) NK cells were preferentially targeted for apoptosis. NK activity was significantly lower in patients with HNC and BC than in NC (p<0.009). An inverse correlation between NK activity and the percent of Anx(+)CD56(dim) NK cells was observed in cancer patients (p =0.002) but not in NC. In patients, circulating CD56(dim) NK cells were targeted for apoptosis, leading to low levels of NK activity.

Low natural killer activity and central nervous system disease as a high-risk prognostic indicator in young patients with hemophagocytic lymphohistiocytosis.

Familial hemophagocytic lymphohistiocytosis HLH (FHL) is fatal, unless patients are rescued with hematopoietic stem cell transplantation (SCT). Although the molecular identification of FHL now is possible at least in part from perforin gene study, many cases escape detection or never are tested due to the lack of specific hallmarks, making diagnosis difficult. To the authors' knowledge, it remains to be determined whether persistently low natural killer cell (NK) activity and a high incidence of central nervous system (CNS) disease increase the probability of FHL. The authors analyzed 42 HLH patients age < 2 years, 13 of whom developed overt CNS disease and 5 of whom demonstrated persistently deficient NK activity (Group 1). The remaining 24 patients had no CNS disease and had NK activity of moderate decrease to within the normal range (Group 2). In Group 1, CNS symptoms were detected in 6 cases within 1 month and between 4.5-9 months in 6 other patients. In these cases, spotty lesions demonstrating a high T2 signal in the white matter were noted on brain magnetic resonance imaging. The survival was significantly poor for patients in Group 1 unless they were rescued with SCT, which was performed in 5 of the 13 patients with CNS disease and in all 5 patients with persistent NK activity deficiency. SCT was successful in 9 patients, with no CNS sequelae reported after the transplantation. Conversely, the prognosis of the 24 patients in Group 2 was better and only 1 patient required SCT. Very young HLH patients (age < 2 years) who are at high risk of fatal FHL with persistently deficient NK activity and/or overt CNS disease require appropriate SCT to reverse CNS disease and achieve a complete cure.

Natural Killer Activity and Thyroid Hormone Levels in Young and Elderly Persons

Background: On the basis that (1) multiple interactions exist between the hormonal and immune systems, and (2) aging is accompanied by changes in thyroid hormone metabolism and responsiveness, we postulate that thyroid hormones may be involved in the observed decrease in natural killer (NK) activity in a population of apparently healthy elderly subjects. The purpose of the study is to compare NK cytotoxic activity and serum concentrations of TSH and thyroid hormones in healthy old and young people, and to assess in vitro the effects of triiodothyronine (T₃) on NK activity. Materials and Methods: Sixteen of the 47 healthy old people (mean age 64 ± 5.2) were classified as optimally healthy, and the remainder as ‘almost healthy’ (according to the criteria of the Senieur protocol) [Ligthart et al., Mech Ageing Dev 1984;28:47–55]; the mean age of the healthy young people was 23.3 ± 2.3 years. NK cytotoxic activity of peripheral blood mononuclear cells was assessed using ⁵¹Cr release from K562 target cells. The cutoff level for defining low and high NK responses was set at a value of 20%. Serum concentrations of TSH, total thyroxine (T₄) and total triiodothyronine (T₃) were measured by radioimmunoassay. Results: NK activity in the ‘optimally healthy’ elderly was high (mean 41 ± 12%, SE), whereas ‘almost healthy’ subjects showed low NK activity (mean 6 ± 5%). Serum T₄ and TSH levels, but not T₃ concentrations were similar in both the young and old. We observed a significant correlation (r = 0.53, n = 21, p < 0.05) between the serum total T₃ level and the NK activity in the elderly individuals. Under in vitro conditions exogenous T₃ significantly increased NK activity in the elderly subjects who had serum T₃ values at the lower end of the reference range. However, no effect of T₃ on NK activity was observed in peripheral blood mononuclear cells obtained from either old or young individuals who had serum T₃ levels at the midpoint of the range. Conclusion: Decreased serum concentrations of total T₃ may contribute to low NK activity in the ‘almost healthy’ subgroup of the elderly.

Intrinsic and environmental influences on immune senescence in the aged monkey

Several factors associated with the age-related decline in immunity were examined in three studies on aged rhesus monkeys. Natural killer (NK) cell activity was found to be low in many monkeys after 20 years of age, but exceptionally long-lived animals, older than 25 years, often had vigorous cytolytic responses. When NK activity was decreased in an aged monkey, it was predictive of fewer years of survival and a younger age at death. This prediction of mortality was associated with one nonimmune biomarker of aging in the monkey: nail growth rate. Monkeys with very slow nail growth and low NK activity were likely to die sooner. Although these findings might suggest an immutable course for the aging process, the housing conditions of old monkeys also had a pronounced effect on their NK activity. The highest NK responses were found in old monkeys housed with just one other old animal when compared to living alone or with just a young, juvenile monkey. It remains to be determined whether this type of psychosocial influence could have a sustained effect on immunity and ultimately change the pace of aging and time to mortality.

Compensatory effect of TNFalpha on low natural killer activity in the elderly.

Regulatory effect of CD25, an activation antigen the alpha subunit of interleukin 2 receptor (IL2R) on the activity of natural killer (NK) cells was studied in fifty elderly (57-70 years old) and fifty young people (19-35 years old). Cytotoxic NK activity was assessed by 51Cr release assay, the levels of interleukin 2 (IL2) and tumour necrosis factors alpha (TNFalpha) were measured using bioassays and expression of CD16 and CD25 proteins by flow cytometry. Low NK activity in the elderly was associated with decline of full health, lowered serum concentration of IL2 and increased production of TNFalpha during NK reaction. Inhibition of TNFalpha activity by anti-TNF monoclonal antibody suppressed exclusively NK activity of low NK responders. Moreover, stimulation in vitro of blood mononuclear cells, with TNFalpha induced in the elderly low NK responders a significantly higher increase of the CD25 expression on the surface of NK cells as compared with that in the elderly high responders. Since the CD25 molecule constitutes a subunit of the high affinity receptor, binding IL2 to immunocompetent cells, its increased expression on NK cells of low NK responders would enable them to bind even low amounts of the endogenous IL2 available in this group of the elderly. Thus, an overproduction of TNFalpha seems to be a mechanism compensating, in the non-fully healthy elderly, for the decreased IL2 production, promoting efficient cytotoxic reaction.

Natural killer activity in mice infected with rabies virus and submitted to P. acnes ( Propionibacterium acnes) as immunomodulator

The natural killer (NK) activity and lethality were evaluated in swiss mice experimentally infected with street rabies virus and submitted to immunomodulation by P. acnes (formerly Corynebacterium parvum). The infected animals were sacrificed at different times and spleen non-adherent cells were obtained through ficoll-hypaque gradient and depletion of glass-adherent cells. Immunosuppression was observed in rabies virus infected mice correlated with lower NK activity in clinically ill animals. Higher NK activity and percentual of survival were observed in the group submitted to P. acnes. The increased survival correlated with higher NK activity induced by P. acnes suggests a protective role of this natural barrier against rabies virus infection in mice.

Circulating natural killer cells in retired asbestos cement workers.

The effect of past exposure to asbestos on natural killer (NK) cell number and activity is uncertain. We measured NK cell number and activity in 1052 retired asbestos workers without symptomatic lung disease, lung cancer, or mesothelioma and with a long latency period from exposure; results were compared with those for 100 healthy age-matched controls. The exposed workers showed a decreased NK cell activity and increased NK cell number, yielding a 10.8 higher odds ratio for low NK activity per cell compared with controls (95% confidence interval 6.4 to 18.4), which was due to both a decrease in NK cell activity and an increase in NK cell number. Asbestos exposure of 10 years or more increased the risk of low NK activity per cell. We conclude that exposure to asbestos is associated with diminished effectiveness of NK cells and a concomitant increase in the number of NK circulating cells.

The immune system in the elderly: III. Innate immunity.

The capability to cope with infectious agents and cancer cells resides not only in adaptive immune responses against specific antigens, mediated by T and B lymphocytes clonally distributed, but also in natural immune reactions. These innate defence mechanisms include chemotaxis, phagocytosis, natural cytotoxicity, cell interactions, and soluble mediators or cytokines. However, specific and natural immune mechanisms are always closely linked and interconnected, providing the primary defense against pathogens. The Authors discuss the main changes observed with advancing age in granulocytes and natural killer (NK) cell activity, in the expression and function of adhesion molecules, and in the pattern of cytokine production. Since phagocytic function is the primary mechanism through which the immune system eliminates most extracellular pathogenic microorganisms, analysis of this function is of clinical importance. Neutrophils from aged subjects often exhibit a diminished phagocytic capacity, as well as a depressed respiratory burst, notwithstanding an activated state. The activity of NK cells during aging has been studied extensively and different results have been reported. The most consistent data indicate an increase in cells with high NK activity with advancing age. Cells from healthy centenarians can efficiently kill target cells. This finding seems to suggest that innate immunity and in particular NK cell activity, is not heavily deteriorated with age. Conversely, a low NK activity is a predictor of impending morbidity. Immunosenescence is associated with increased expression of several cell adhesion molecules (CAM) resulting in an augmented capacity to adhere. Finally, also the cytokine network, responsible for differentiation, proliferation, and survival of lymphoid cells, undergoes complex changes with age. The main findings are a Th1 to Th2 cytokine production shift and an increased production of proinflammatory cytokines, which could explain many aspects of age-associated pathological events, such as atherosclerosis and osteoporosis.

Progesterone-induced blocking factor inhibits degranulation of natural killer cells.

During the first trimester of pregnancy, nonclassical (CD3-, CD56+, CD16-, perforin [P]bright+) natural killer (NK) cells comprise the major decidual lymphocyte population. These cells, in spite of their high perforin content, exert a low cytolytic activity. Peripheral blood lymphocytes of healthy pregnant women produce progesterone-induced blocking factor (PIBF), which inhibits NK activity. PIBF-producing cells are likely to be present in decidua and might contribute to low decidual NK activity. Decidual cells obtained from elective pregnancy termination were double labeled for CD56 and PIBF. We tested the effect of PIBF on perforin liberation by activated peripheral blood NK cells. Sixty percent of decidual lymphocytes were CD56 + and expressed PIBF at the same time. PIBF-treated and untreated peripheral blood NK cells were incubated with K-562 cells, and perforin content of target conjugated NK cells was detected with immunocytochemistry. PIBF treatment of peripheral blood lymphocytes significantly reduced lysis of K-562 cells. Among target bound lymphocytes in PIBF-treated samples, we found a significantly (P < 0.01) higher rate of P+ cells than in untreated samples. These data suggest that PIBF inhibits cytotoxicity of NK cells via a block of degranulation, and since decidual NK cells are PIBF+, it cannot be ruled out that this effect of PIBF contributes to low decidual NK activity.

The role of gamma/delta T cells in progesterone-mediated immunomodulation during pregnancy: a review.

To determine if pregnancy is recognized by the immune system and if inadequate recognition of fetal antigens might result in failed pregnancy. Review of literature and current data. In the decidua gamma/delta TCR positive cells significantly increase in number. A subset of gamma/delta T cells reacts with nonpolymorphic Class I or Class I like molecules. Trophoblast recognition is mediated by the V gamma 1 subset which recognize a conserved mammalian sequence on the trophoblast. Almost all gamma/delta T cells in the decidua are activated and use the V delta 1 chain, whereas the majority of human peripheral gamma/delta lymphocytes expresses V gamma 9/V delta 2 TCR. Peripheral gamma/delta T cells of healthy pregnant women preferentially use V gamma V delta 1 chains, on the other hand, those of recurrent aborters use the V gamma 9V delta 2 combination. Signaling via the V gamma 1.4V delta 1 receptor induces a Th2 type response, whereas activation of the lymphocytes via the V gamma 9V delta 2 receptor results in increased IL-12 production and natural killer (NK) activity. In the presence of progesterone, activated lymphocytes synthesize the progesterone induced blocking factor (PIBF), which inhibits NK activity and exerts an anti abortive effect in vivo. Decidual CD56+ and gamma delta+ cells are to a high extent the same population. All decidual CD56+ cells express PIBF, thus it cannot be excluded that local production of this substance contributes to low decidual NK activity and thus to the success of the pregnancy.

Differential cytokine regulation of natural killer cell-mediated necrotic and apoptotic cytotoxicity.

Natural killer (NK) cells can kill target cells by either necrotic or apoptotic mechanisms. Using the 51Cr-release assay to measure necrotic death of target cells, neonatal NK cells had low NK activity (K562 targets) and high lymphokine-activated killer (LAK) activity (Daudi targets) compared with adult cells, as has been previously reported. Using a 125I-deoxyuridine (125I-UdR) release assay, cord cells were shown to also have higher apoptotic LAK activity against YAC-1 target cells. Interleukin-4 (IL-4) inhibited interleukin-2 (IL-2)-induced necrotic killing of target cells by adult effectors but had no such inhibitory effect on cord cells. In contrast, IL-4 inhibited both adult and cord LAK cytotoxicity of YAC-1 target cells by apoptotic mechanisms with higher suppression observed in cord cell preparations. Using a colorimetric substrate conversion assay, IL-2 induced higher, and IL-4 had a more significant suppressive effect on, cord cell granzyme B enzyme activity compared with adult cells, paralleling apoptosis cytotoxicity data. Co-culture of either adult or cord LAK cells with IL-4 had a similar inhibitory effect on granzyme B protein expression, as detected by Western blotting. In contrast, IL-4 did not inhibit perforin expression, thereby defining IL-4 as a cytokine that can differentially regulate the NK cell-mediated cytotoxicity processes of apoptosis and necrosis. The differential sensitivity of cord cells to cytokine regulation of cytotoxicity may also have implications for cord blood transplantations, as NK cells are known to function as an effector cell in both graft-versus-host disease and in the graft-versus-leukaemia phenomena.