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Effect of Zinc Supplementation on the Immune Status of Healthy Older Individuals Aged 55–70 Years: The ZENITH Study

¹ Northern Ireland Centre for Food and Health (NICHE), University of Ulster, Coleraine, Northern Ireland.
² Department of Haematology, Belfast City Hospital, Northern Ireland.
³ Centre de Recherche en Nutrition Humaine d'Auvergne, Unité Maladies Métaboliques et Micro-nutriments INRA, Centre de Recherche de Clermont-Ferrand, Saint Genès Champanelle, France.

Address correspondence to Julie M. W. Wallace, PhD, Northern Ireland Centre for Food and Health (NICHE), University of Ulster, Coleraine, Northern Ireland BT52 1SA. E-mail: j.wallace{at}ulster.ac.uk

	Abstract

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Aging is associated with alterations in the immune system, effects which may be exacerbated by inadequate zinc (Zn) status. We examined the relationship between Zn status and markers of immunity and the effect of supplementation with 15 mg or 30 mg Zn/d for 6 months on immune status in healthy individuals. Zn status was assessed by dietary intake and biochemical indices. Immune status was assessed by multiple flow cytometric methods. At baseline, Zn concentration was positively associated with lymphocyte subpopulation counts and T-lymphocyte activation. Zn supplementation of 30 mg/d significantly lowered B-lymphocyte count, albeit at month 3 only. Lower doses of Zn (15 mg Zn/d) significantly increased the ratio of CD4 to CD8 T lymphocytes at month 6. Overall, these findings suggest that total Zn intake (diet plus supplementation) of up to 40 mg Zn/d do not have significant long-term effects on immune status in apparently healthy persons aged 55–70 years.

It has been suggested that the achievement of optimal nutritional status may help to alleviate the stress placed on the aging immune system, allowing for successful aging (10). One trace element that has been identified as essential for the maintenance and optimal functioning of the immune system is zinc (Zn). Zn deficiency has been shown to result in depressed innate and adaptive immunity—specifically, reduced antibody production, lymphocyte proliferation in response to mitogen stimulation, and decreased CD4+/CD8+ ratios. These conditions can be reversed by Zn supplementation [see reviews (11–14)].

To date, however, the majority of studies on Zn and immune function have focused on infectious disease in childhood (15–19) or in elderly populations (20–26). These studies have demonstrated that higher Zn intakes are associated with improved resistance to infection, symptomatic relief, and reduced duration of illness; as well as improvements in antibody titer, delayed hypersensitivity reaction, and specific lymphocyte subpopulation numbers. Other studies investigating immune status have been based on selected samples of aging volunteers or on clinically based samples, e.g., Senieur project of EURAGE (27). However, there is a distinct lack of studies that have examined the relationship between Zn status and immune status in healthy older people at risk for suboptimal Zn status such as late-middle-aged persons. It is estimated that dietary Zn intakes in 50% of 51- to 70-year-olds in Western populations fall below the recommended dietary allowance, indicating that this population may be at risk of suboptimal Zn status (28). It is unclear, however, at what point suboptimal Zn status may become deleterious to immune status and, consequently, health.

Although the deleterious effects of age have been more consistently reported with respect to adaptive immunity (6–9), we have previously reported that age-related alterations occur in markers of both innate and adaptive immunity in the current study population and, importantly, that such changes are largely sex specific (29). We hypothesized, given the findings of previous research (15–26), that specific markers of adaptive immune status such as B lymphocytes, naïve and memory T lymphocyte subsets, natural killer (NK) cells, the CD4/CD8 ratio, and intracellular cytokine production would respond to Zn supplementation. Other functional and phenotypic markers of immunity, for which there is less evidence of an effect of Zn, were included as secondary outcomes. There is no single marker that can provide a definitive picture of an individual's immune competence. Therefore, in the current study, an extensive panel of phenotypic markers of immunity were included to provide comprehensive information on immune status (as defined by numbers of circulating lymphocyte subsets), and to facilitate the interpretation of an array of functional assays; important given that functional assays are associated with clinical endpoints and present a mechanistic understanding of the immune response (30).

Consequently, the aim of the current study was to assess the associations between putative indices of Zn status and markers of immunity and to examine the effect of Zn supplementation on a comprehensive range of phenotypic and functional immune markers in free-living, apparently healthy late-middle-aged men and women, aged 55–70 years.

	METHODS

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Study Population
A total of 147 individuals, aged 55–70 years (77 women, 70 men) were recruited from across Northern Ireland through media coverage, leaflets, and the cooperation of national and local organizations with members spanning the age group of interest. Of the 147 persons recruited, 101 apparently healthy individuals were invited to participate in the study based on defined exclusion criteria, including: body mass index (BMI) < 20 or > 33 kg/m²; abnormal hematology, liver function, or kidney function; unusual dietary habits (e.g., vegetarian and vegan); current acute or chronic disease; poor neuropsychological performance; use of immune modulating medications, habitual use of vitamin and/or mineral supplements in the last 6 months; alcohol consumption of > 30 g/d (for men) or > 20 g/d (for women); and smoking > 10 cigarettes, cigars, or pipes per day. All the women recruited were postmenopausal (>12 months since their last menses) and were not receiving hormone replacement therapy. The University of Ulster Research Ethical Committee granted approval for the study. All volunteers gave informed signed consent in accordance with the declaration of Helsinki.

Study Design
The study design was a double-blind, randomized, placebo-controlled intervention. Volunteers were recruited over a 3-month period from March and were randomly assigned to receive either 15 mg/d or 30 mg/d of elemental Zn (as Zn gluconate) or an identical placebo capsule for 6 months. Supplements were supplied by E-Pharma (Ganna, France).

Collection of Peripheral Blood and Hematological Analysis
Following an overnight (>12 hours) fast, participants were asked to arrive at the research center at 8:30 AM on the study day. Body weight and height were measured at baseline, and BMI was calculated.

Blood and urine samples were collected from volunteers at baseline, at month 3, and at month 6 of the intervention. Venous anticoagulated blood (55 mL) was collected in K₃EDTA, lithium–heparin, sodium–heparin anticoagulated Vacutainer tubes and serum separator tubes. K₃EDTA whole blood was used for determination of immune status on a FACSCalibur flow cytometer (BD Biosciences, Oxford, U.K.) within 4 hours of sample collection. K₃EDTA whole blood was also used to assess full blood profile (conducted at Causeway Laboratory, Causeway NHSS Trust, Coleraine, Northern Ireland). Plasma, erythrocytes, and serum were separated and stored at –80°C until analysis at the end of the study.

Trace Element Intake, Markers of Trace Element Status, and Measures of Inflammation
Dietary Zn, copper (Cu), and iron (Fe) intakes were assessed using a semiquantitative food diary. Participants were asked to record every item of food and drink consumed over four consecutive days. Amounts consumed were recorded in terms of household measures and units of food (e.g., slices of bread, cans of soda), and published standard food weights for the U.K. were used to convert these quantities to gram weights (31). Nutrient intakes were analyzed using the Weighed Intake analysis Software Package (WISP) 2.0 for Windows (Tinuviel Software, Warrington, U.K.), based on U.K. food composition data.

Serum, erythrocyte, and urinary Zn concentrations were determined by flame atomic absorption spectrometry on a Perkin Elmer 560 analyzer at Grenoble University Hospital, France. Urinary creatinine concentration was assessed by colorimetry, as previously described (32). Alkaline phosphatase (ALP) was analyzed using a commercially available kit (Roche Diagnostics, Lewes, U.K.) on a Hitachi 912 autoanalyzer (Roche Diagnostics). Hemoglobin (Hb), ferritin, and transferrin saturation were assessed as measures of Fe status. Hb was determined at Causeway Laboratory, Causeway NHSS Trust, and ferritin and transferrin saturation were analyzed by immunonephelometry at Grenoble University Hospital. Erythrocyte Zn-Cu superoxide dismutase activity (RBC SOD) and serum ceruloplasmin (CP) were assessed as putative indicators of Cu status. RBC SOD was analyzed using a commercially available kit (Randox, Crumlin, U.K.), and CP was determined by turbidimetry (DakoCytomation, Ely, U.K.) on a Hitachi 912 autoanalyzer (Roche Diagnostics). Serum C-reactive protein (CRP), complement protein-3 (C3), and complement protein-4 (C4), were determined using commercially available kits (Roche Diagnostics) on a Hitachi 912 autoanalyzer.

Markers of Immunity
The panel of fluorochrome-conjugated monoclonal antibodies used in the current study for immunophenotyping, apoptosis, phagocytosis, and intracellular cytokine assays as performed by flow cytometry has been previously described by Hodkinson and colleagues (29). Immunophenotyping was performed as previously described by Hodkinson and colleagues (33).

The determination of early lymphocyte apoptosis by two-color flow cytometry was conducted using an Annexin V-FITC Apoptosis Detection Kit I (BD Biosciences). Briefly, peripheral blood mononuclear cells (PBMC) were separated by density gradient centrifugation from sodium–heparin anticoagulated whole blood using ACCUSPIN System Histopaque 1077 tubes (Sigma-Aldrich, Dorset, U.K.). PBMC were washed twice in fresh sterile filtered phosphate-buffered saline (PBS) and then resuspended in binding buffer (BD Biosciences). PBMC were stained using Annexin V-FITC and propidium iodide (PI). Lymphocytes were gated using a forward-scatter (FSC) versus side-scatter (SSC) dotplot. Lymphocytes staining positive for Annexin-V FITC and negative for PI were determined using fluorescence channel 1 height (FL1-H) versus fluorescence channel 2 height (FL2-H) dotplots. The percentage of lymphocytes undergoing early apoptosis was obtained from fluorescence-activated cell sorter (FACS) analysis, and absolute counts were calculated using the lymphocyte white blood cell differential (x 10⁹/L).

The quantification of phagocytic capacity and activity of granulocytes and monocytes were determined using a PhagoTest kit (Orpegen Pharma, Heidelberg, Germany). Sodium–heparin whole blood (100 µL) was incubated with opsonized Escherichia coli–FITC. Monocytes and granulocytes were gated using FSC versus SSC dotplot. SSC versus E. coli–FITC dotplots were used to measure phagocytic capacity and activity for both cell types. The percentage of E. coli–FITC–positive cells provided a measure of phagocytic capacity. Mean fluorescence intensity (MFI) was used to quantify the mean number of E. coli ingested per cell, as a determinant of phagocytic activity.

Intracellular cytokine production by activated monocytes was based on a previously described method by McNerlan and colleagues (34). Briefly, 1 mL of sodium–heparin whole blood was incubated with lipopolysaccharide (LPS) at 1 µg/mL and Brefeldin A (BFA) at 10 µg/mL (Sigma-Aldrich). After incubation, 100 µL of activated blood was incubated with either 10 µL of immunoglobulin G (IgG) 2 FITC (isotype control) or CD14 FITC (BD Pharmingen, Oxford, U.K.). Erythrocytes were lysed, the remaining cells were washed and centrifuged, and the cell pellet was resuspended with 100 µL of permeabilizing medium B (Caltag, Invitrogen, Paisley, U.K.). IgG1 phycoerythrin (PE; isotype control), interleukin-1ß (IL-1ß) PE, or IL-6 PE (10 µL) was added for a further incubation. Cells were washed and fixed with 500 µL of 1x Cell Fix solution (BD Biosciences). Samples were analyzed immediately.

Monocytes were gated using FSC versus SSC dotplots, and percentages of cytokine-positive CD14 cells were obtained from FL-1 H versus FL-2 H dotplots. Intracellular cytokine production, as determined by the antibody binding capacity (ABC), was quantified using PE QuantiBRITE beads (BD Biosciences) for standardization of PE MFI.

Statistical Analysis
Statistical analyses were performed using the Statistical Package for Social Sciences (SPSS) version 11.0. Markers of immune status did not display normal distribution and, therefore, were normalized as appropriate prior to analysis. Partial correlations were used to analyze associations between serum and erythrocyte Zn concentration and immune status, controlling for age (p .05). Repeated-measures analysis of variance (ANOVA) was used to determine the effect of Zn supplementation on immune status, in Zn and control groups (p .05), with sex, age, and the appropriate baseline variable as covariates. In this procedure, responses at month 3 and month 6 were used as within-subject variables, and treatment was used as the between-subject factor. The main effect of treatment was compared by using Bonferroni's procedure for confidence interval (CI) adjustment.

	RESULTS

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Participant Characteristics
A total of 93 apparently healthy individuals completed the intervention; 31 in the placebo group, 28 in the 15 mg Zn/d group, and 34 in the 30 mg Zn/d group. The mean (± standard error of the mean [SEM]) age was 62.4 (± 0.47) years. Table 1 shows the mean (± SEM) for baseline characteristics for each treatment group. No significant differences were seen among groups at baseline in any of the variables. Serum Zn, erythrocyte Zn, urinary Zn/creatinine ratio and ALP concentrations were all within the normal adult reference ranges. Mean (± SEM) Hb, ferritin, transferrin saturation, RBC SOD, and CP were 14.5 (± 0.13) g/dL, 93.0 (± 7.49) µg/L, 30.2 (± 1.14)%, 1011 (± 21.7) U/g Hb, and 0.21 (± 0.004) U/L at baseline, respectively. No significant differences were observed among groups for putative measures of Fe and Cu status at baseline (data not shown). Immune status as assessed by immunophenotyping was within normal reference ranges and comparable to that reported by McNerlan and colleagues (35), who examined a similar population from Northern Ireland, and by Bisset and colleagues (36), who assessed immune status in healthy 19- to 70-year-olds in Switzerland.

There was no significant Time x Treatment interaction of Zn supplementation on Hb, ferritin concentration, transferrin saturation, or CP. RBC SOD showed a significant (p =.046) within-subject Time x Treatment interaction and a significant between-subject (p =.043) treatment effect, where individuals receiving 30 mg Zn/d had higher RBC SOD than did those receiving 15 mg Zn/d at month 3 only.

Effect of Zn Supplementation on Markers of Inflammation
Mean (± SEM) serum CRP, C3, and C4 for all participants were 0.20 (0.04) mg/dL, 1.28 (0.02) g/L, and 0.26 (0.01) g/L, respectively. C3 and C4 concentrations were within the normal adult reference ranges. Although 10 individuals had subclinical inflammation, as indicated by elevated serum CRP concentration (> 0.5 mg/dL), no significant interaction or supplementation effects were observed for C3, C4 complement proteins, or CRP concentration (data not shown).

Effect of Zn Supplementation on Leukocyte Subpopulations
The percent expression and absolute counts of leukocyte and lymphocyte subpopulations in peripheral whole blood were within normal adult ranges, and the Time x Treatment interactions for Zn supplementation can be seen in Table 3 (% expression) and Table 4 (absolute counts).

For percent expression of B lymphocytes, within-subject effects showed a nonsignificant Time x Treatment interaction (p =.051), as shown in Table 3. However, a significant main effect of treatment (p =.028) was seen, whereby the percent expression of B lymphocytes was significantly lower (p =.045) in the 30 mg Zn/d group than in the placebo group. For the B-lymphocyte absolute count (x 10⁹/L), within-subject effects showed a significant Time x Treatment interaction (p =.028; see Table 4) and a significant treatment effect (p =.016). The absolute count of B lymphocytes was significantly lower (p =.001) in the 30 mg Zn/d group than in the 15 mg Zn/d group, at month 3 only. There was no significant Time x Treatment interaction on the percent expression (Table 3), or absolute count of lymphocytes in early apoptosis (Table 4).

For the (CD3+/CD4+: CD3+/CD8+) T helper to T-cytotoxic lymphocyte (CTL) ratio responses, within-subject effects showed a significant Time x Treatment interaction (p =.026), where the T helper/CTL ratio in the 15 mg Zn/d group at month 6 was significantly higher (p =.043) than in the placebo group (see Table 4).

Effect of Zn Supplementation on Phagocytosis and Intracellular Cytokine Production in Activated Monocytes
Repeated-measures ANOVA showed no significant Time x Treatment interaction or main effect of treatment on the phagocytic capacity (%) or activity (MFI) of either granulocytes or monocytes (Table 5). There was no significant Time x Treatment interaction and no effect of treatment on the percent expression of either IL-1ß or IL-6 and ABC by activated monocytes (Table 6).

	DISCUSSION

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The present study was undertaken to evaluate the associations between putative indices of Zn status and markers of immune status and to determine the effect of Zn supplementation on selected markers of immunity in apparently healthy individuals aged 55–70 years. Mean estimated dietary intake at baseline was 9.28 mg Zn/d, just below the U.K. reference nutrient intake of 9.5 mg Zn/d (37), and comparable with intakes previously reported (38). Thus, the upper level of Zn intake (at supplementation of 30 mg Zn/d) was approximately 40 mg/d for participants in the current study, which exceeds the European tolerable upper level (UL) of 25 mg Zn/d, and is equivalent to the UL in the United States (39,40).

At baseline, erythrocyte Zn concentration was inversely associated with granulocyte phagocytic capacity and positively associated with T-lymphocyte subsets, markers of T-lymphocyte activation, and NKT cell numbers. These findings suggest that a higher cellular Zn concentration maintains T-lymphocyte populations, and that such immune cells may be more readily primed for response to exogenous stimuli. Human circadian rhythms demonstrate high morning cortisol concentration, high Zn concentrations, and low phagocytic activity, with respective decreases and increases during the course of the day (41,42). This observation is further supported by our finding of a significant inverse association between morning erythrocyte Zn concentration and granulocyte phagocytic capacity. During periods of acute and/or chronic inflammation, Zn is redistributed from the labile serum pool to other body compartments, e.g., liver and erythrocytes (43–46). The redistribution of Zn during inflammation is supported by our observation of an inverse association between serum Zn concentration and the inflammatory marker CRP. In addition, IL-2 receptor density on T lymphocytes was positively associated with serum Zn. As IL-2 receptor density is associated with T-lymphocyte activation (47), this may explain why T-lymphocyte activation is dependent on Zn concentration. Overall, the current study emphasizes that, in the absence of a sensitive clinical indicator of Zn status (48), the measurement of Zn concentration in multiple body compartments is recommended to explore adequately the relationship between Zn and immune status. Future studies examining the influence of Zn status on immune function should also consider using neutrophil and/or lymphocyte Zn concentration and associated measures of Zn metallothionein in immune cells (49,50).

Postsupplementation, the percent expression of naïve T lymphocytes, the absolute count of monocytes and B lymphocytes, and T helper/CTL ratio showed significant Time x Treatment interactions with Zn. However, only B lymphocytes and T helper/CTL ratios demonstrated a significant main effect of treatment, suggesting that the Time x Treatment interactions observed for other parameters were largely driven by seasonal effects on immune function (51–55).

If confirmed, the finding that B-lymphocyte counts were significantly lower in the 30 mg Zn/d group compared to the 15 mg Zn/d and placebo groups at month 3 only potentially indicates a negative influence of high doses of Zn supplementation, which may be of particular concern in older individuals vulnerable to immune deficiencies. The efficiency of humoral immunity is reduced with age (56–59), which results in decreased effectiveness of vaccination (60,61), increasing the susceptibility to, and mortality from, infection. A positive relationship between Zn nutrition and antibody titer postvaccination in the elderly population has been reported in some (62), but not all studies (63,64). The potential negative effect of higher doses of Zn supplementation (30 mg Zn/d) in non-Zn-deficient individuals requires confirmation. Furthermore, it will be important to clarify further the effect of Zn supplementation on humoral immunity and response to vaccination in aged individuals.

The T helper/CTL ratio has been reported to decline with age, and to be a predictor of survival in old age (65,66). Postsupplementation at month 6, individuals receiving 15 mg Zn/d had significantly higher T helper/CTL ratios compared to the placebo group, suggesting that longer term Zn supplementation at a moderate dose (15 mg Zn/d) may result in maintenance of these lymphocyte subpopulations with age. Measurement of a large number of parameters increases the likelihood of chance findings; therefore, further investigation is required to confirm the effects of Zn supplementation in healthy individuals observed in the current study. No significant effect of Zn supplementation on the functional markers of immunity, phagocytosis and intracellular cytokine production by activated monocytes, were observed in this study, possibly owing to the apparent lack of Zn deficiency in the study population.

Previous studies have shown that marginal Zn status in elderly individuals (70 years) is associated with decreased immunity (25,67) and that Zn supplementation restores immune responses in this age group (20,21,24,68,69). These findings are in contrast to our results, where only B lymphocytes and the T helper/CTL ratio appeared responsive to Zn supplementation. However, our finding of an overall lack of effect of supplementation on immune status is supported by other previous studies, which reported little effect of Zn supplementation in young adult men (38) and elderly individuals (aged 64–100 years) (63).

However, one major limitation that plagues all studies of Zn supplementation is the lack of a specific and sensitive marker of Zn status. Indeed in the current study, only one of the putative markers of Zn status, serum Zn, increased postsupplementation, and this was only evident in the 30 mg Zn/d treatment group. However, participants in the group receiving 30 mg Zn/d demonstrated significantly higher urinary Zn/creatinine ratios compared to the group receiving 15 mg Zn/d. This finding (if confirmed) would suggest that, in apparently healthy individuals, supplemental doses of 30 mg Zn/d might exceed requirements. The tight regulation of Zn homeostasis within the body is well known, and this may partly explain why individuals with apparently adequate dietary intakes of Zn did not demonstrate enhancement of immune status postsupplementation. Although adequate Zn status at baseline may be a key factor, we cannot rule out the possibility that other aspects of immunity not assessed in those individuals studied may have responded to Zn supplementation.

The results of the current study contribute to the limited scientific literature examining the effect of Zn supplementation at the UL and no observed adverse effect level (NOAEL) on immune status (39,40). To our knowledge, this is the first trial to examine such effects in this age group. Supplementation with 30 mg Zn/d has previously been reported to have no negative effect on putative measures of Cu status (38), a finding largely supported by our results.

Conclusion
Zinc supplementation appears to have a differential response on humoral and cell-mediated immunity in healthy older adults with near adequate dietary Zn intake. Moderate Zn supplementation at the level of 15 mg/d may help to maintain the T helper/CTL ratio and consequently enhance adaptive immunity; however, higher doses of supplementation in the region of 30 mg/d may affect B-lymphocyte counts, exacerbating age-related changes. Further intervention studies should focus on the effects of Zn on other aspects of immunity, with relevance to an aging population, such as response to vaccination.

	Acknowledgments

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This work was supported by the European Commission ‘Quality of Life and Management of Living Resources' Fifth Framework Program, Contract No: QLK1-CT-2001-00168, and by the Department of Education and Learning (DELNI), U.K.

We thank Dr. E. E. A. Simpson, School of Psychology, University of Ulster, for her role in participant recruitment and application of health and lifestyle and psychosocial questionnaires; the Causeway Laboratory, Causeway NHSS Trust, Coleraine, Northern Ireland for their analysis of full blood profiles; Dr. J. L. Lafond, Grenoble University Hospital, France, for his analysis of serum ferritin and transferrin saturation; and Mary Toohey, The Northern Ireland Clinical Research Support Centre (CRSC), Education and Research Centre, Royal Group of Hospitals Trust, Belfast for her advice and assistance with statistical analysis. We gratefully acknowledge the participation the participants in the study. C. F. H. was responsible for study execution, data analysis, and writing of the manuscript. M. K. assisted with study execution. C. C. was the coordinator of the ZENITH study and was responsible for analysis of biological zinc indices. I. B. provided statistical advice. H. D. A. provided advice on flow cytometry methodology and assisted in the preparation of the manuscript. P. J. R., J. M. O. M. P. B., J. J. S., and J. M. W. W. were responsible for study design, supervised study execution and data analysis, and assisted with preparation of the manuscript.

	Footnotes

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Decision Editor: Huber R. Warner, PhD

Received March 24, 2006

Accepted January 30, 2007

	References

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1. Castle SC. Clinical relevance of age-related immune dysfunction. Clin Infect Dis. 2000;31:578-585.[Medline]
2. Gomez CR, Boehmer ED, Kovacs EJ. The aging innate immune system. Curr Opin Immunol. 2005;17:457-462.[Medline]
3. Haynes BF, Sempowski GD, Wells AF, Hale LP. The human thymus during aging. Immunol Res. 2000;22:253-261.[Medline]
4. Licastro F, Candore G, Lio D, et al. Innate immunity and inflammation in ageing: a key for understanding age-related diseases. Immun Ageing. 2005;2:8.[Medline]
5. Plackett TP, Boehmer ED, Faunce DE, Kovacs EJ. Aging and innate immune cells. J Leukoc Biol. 2004;76:291-299.[Abstract/Free Full Text]
6. Burns EA, Goodwin JS. Effects of aging on immune function. J Nutr Health Aging. 2004;8:9-18.[Medline]
7. Thoman ML. Effects of the aged microenvironment on CD4+ T cell maturation. Mech Ageing Dev. 1997;96:75-88.[Medline]
8. Fulop T, Larbi A, Wikby A, Mocchegiani E, Hirokawa K, Pawelec G. Dysregulation of T-cell function in the elderly: scientific basis and clinical implications. Drugs Aging. 2005;22:589-603.[Medline]
9. Chakravarti B, Abraham GN. Aging and T-cell-mediated immunity. Mech Ageing Dev. 1999;108:183-206.[Medline]
10. Paolisso G, Barbieri M, Franceschi C. Metabolic age modelling: the lesson from centenarians. Eur J Clin Invest. 2000;30:888-894.[Medline]
11. Shankar AH, Prasad AS. Zinc and immune function: the biological basis of altered resistance to infection. Am J Clin Nutr. 1998;68:447S-463S.[Abstract]
12. Rink L, Gabriel P. Zinc and the immune system. Proc Nutr Soc. 2000;59:541-552.[Medline]
13. Rink L, Gabriel P. Extracellular and immunological actions of zinc. Biometals. 2001;14:367-383.[Medline]
14. Ibs KH, Rink L. Zinc-altered immune function. J Nutr. 2003;133:1452S-1456S.[Abstract/Free Full Text]
15. Bahl R, Bhandari N, Hanbridge KM. Plasma zinc as a predictor of diarrhoeal and respiratory morbidity in children in an urban slum setting. Am J Clin Nutr. 1998;68:414S-417S.[Abstract]
16. Wieringa FT, Diijkhuizen MA, West CE, Northrop-Clewes CA, Muhilal-van der Meer JWM. Estimation of the effect of the acute phase response on indicators of micronutrient status in Indonesian infants. J Nutr. 2002;132:3061-3066.[Abstract/Free Full Text]
17. Black RE. Zinc deficiency, infectious disease and mortality in the developing world. J Nutr. 2003;133:1485S-1489S.[Abstract/Free Full Text]
18. Duggan C, MacLeod WB, Krebs NF, et al. Plasma zinc concentrations are depressed during the acute phase response in children with Falciparum malaria. J Nutr. 2005;135:802-807.[Abstract/Free Full Text]
19. Rahman MJ, Sarker P, Roy SK, et al. Effects of zinc supplementation as adjunct therapy on the systematic immune responses in shigellosis. Am J Clin Nutr. 2005;81:495-502.[Abstract/Free Full Text]
20. Duchateau J, Delepesse G, Vrijins R, Collet H. Beneficial effects of oral zinc supplementation on the immune response of old people. Am J Med. 1981;70:1001-1004.[Medline]
21. Bogden JD, Oleske JM, Lavenhar MA, et al. Zinc and immunocompetence in elderly people: effects of zinc supplementation for 3 months. Am J Clin Nutr. 1988;48:655-663.[Abstract/Free Full Text]
22. Prasad AS, Fitzgerald JT, Hess JW, Kaplan J, Pelen F, Dardenne M. Zinc deficiency in elderly patients. Nutrition. 1993;9:218-224.[Medline]
23. Lesourd B, Mazari L. Nutrition and immunity in the elderly. Proc Nutr Soc. 1999;58:685-695.[Medline]
24. Ravaglia G, Forti P, Maioli F, et al. Effect of micronutrient status in natural killer cell immune function in healthy free-living subjects aged 90 y. Am J Clin Nutr. 2000;71:590-598.[Abstract/Free Full Text]
25. Bogden JD. Influence of zinc on immunity in the elderly. J Nutr Health Aging. 2004;8:48-54.[Medline]
26. Lesourd B. Nutrition: a major factor influencing immunity in the elderly. J Nutr Health Aging. 2004;8:28-37.[Medline]
27. Ligthart GJ, van Vlokhoven PC, Schuit HRE, Hijmans W. The expanded null cell compartment in ageing: increase in the number of natural killer cells and changes in T-cell and NK-cell subsets in human blood. Immunology. 1986;59:353-357.[Medline]
28. Briefel RR, Bialostosky K, Kennedy-Stephenson J, McDowell MA, Erwin RBR, Wright JD. Zinc intake of the U.S. population: findings from the third National Health and Nutrition Examination Survey, 1998–1994. J Nutr. 2000;130:1367S-1373S.[Abstract/Free Full Text]
29. Hodkinson CF, O'Connor JM, Alexander HD, et al. Whole blood analysis of phagocytosis, apoptosis, cytokine production and leukocyte subsets in healthy older men and women: the ZENITH study. J Gerontol Biol Sci Med Sci. 2006;61A:907-917.[Abstract/Free Full Text]
30. Albers R, Antoine J-M, Bourdet-Sicard R, et al. Markers to measure immunomodulation in human nutrition intervention studies. Br J Nutr. 2005;94:452-481.[Medline]
31. Crawley H. Food Portion Sizes. 3rd ed. London: HM Stationery Office; 1994.
32. Hill T, Meunier N, Andriollo-Sanchez M, et al. The relationship between the zinc nutritive status and biochemical markers of bone turnover in older European adults: the ZENITH study. Eur J Clin Nutr. 2005;59:S73-S78.[Medline]
33. Hodkinson CF, Kelly M, Coudray C, et al. Zinc status and age-related changes in peripheral blood leukocyte subpopulations in healthy men and women aged 55-70 y: the ZENITH study. Eur J Clin Nutr. 2005;59:S63-S67.[Medline]
34. McNerlan SE, Rea IM, Alexander HD. A whole blood method for measurement of intracellular TNF-alpha, INF-gamma and IL-2 expression in stimulated CD3+ lymphocytes: differences between young and elderly subjects. Exp Gerontol. 2002;37:227-234.[Medline]
35. McNerlan SE, Alexander HD, Rea IM. Age-related reference intervals for lymphocyte subsets in whole blood of healthy individuals. Scand J Clin Lab Invest. 1999;59:89-92.[Medline]
36. Bisset LR, Lung TL, Kaelin M, Ludwig E, Dubs RW. Reference values for peripheral blood lymphocyte phenotypes applicable to the healthy adult population in Switzerland. Eur J Haematol. 2004;72:203-212.[Medline]
37. Department of Health. Dietary Reference Values for Food, Energy and Nutrients for the United Kingdom. London: HM Stationery Office; 1991.
38. Bonham M, O'Connor JM, Alexander HD, et al. Zinc supplementation has no effect on circulating levels of peripheral blood leucocytes and lymphocyte subsets in healthy adult men. Br J Nutr. 2003;89:695-703.[Medline]
39. Scientific Committee on Food. Opinion of the Scientific Committee on Food on the tolerable upper intake level of Zinc. Brussels, Belgium: European Commission; 2003;1–18.
40. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chronium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vandium, and Zinc. Washington D.C.: National Academies Press; 2000.
41. Couturier E, Onderbergen A, Bosson D, Neve J. Circadian variations in plasma zinc and cortisol in man. J Trace Elem Electrolytes Health Dis. 1988;2:245-249.[Medline]
42. Melchart D, Martin P, Hallek M, Holzmann M, Jurcic X, Wagner H. Circadian variation of the phagocytic activity of polymorphonuclear leukocytes and of various other parameters in 13 healthy male adults. Chronobiol Int. 1992;9:35-45.[Medline]
43. Beisel WR. Infection-induced malnutrition: from cholera to cytokines. Am J Clin Nutr. 1995;62:813-819.[Abstract/Free Full Text]
44. Clohessy PA, Golden E. Microbiostatic activity of human plasma and its relation to zinc and iron availability. Biochem Soc Trans. 1996;24:311S-312S.[Medline]
45. Giacconi R, Cipriano C, Muzzioli M, Gasparini N, Orlando F, Mocchegiani E. Interrelationships among brain, endocrine and immune response in ageing and successful ageing: role of metallothionein III isoform. Mech Ageing Dev. 2003;124:371-378.[Medline]
46. Cipriano C, Giacconi R, Muzzioli M, et al. Metallothionein (I + II) confers, via c-myc, immune plasticity in oldest mice: model of partial hepatectomy/liver regeneration. Mech Ageing Dev. 2003;124:877-886.[Medline]
47. Scheffold A, Huhn J, Hofer T. Regulation of CD4+CD25+ regulatory T cell activity: it takes (IL-)two to tango. Eur J Immunol. 2005;35:1336-1341.[Medline]
48. Wood RJ. Assessment of marginal zinc status in humans. J Nutr. 2000;130:1350S-1354S.[Abstract/Free Full Text]
49. Sullivan VK, Burnett FR, Cousins RJ. Metallothionein expression is increased in monocytes and erythrocytes of young men during zinc supplementation. J Nutr. 1998;128:707-713.[Abstract/Free Full Text]
50. Allan AK, Hawksworth GM, Woodhouse LR, Sutherland B, King JC, Beattie JH. Lymphocyte metallothionein mRNA responds to marginal zinc intake in human volunteers. Br J Nutr. 2000;84:747-756.[Medline]
51. Abo T, Kumagai K. Studies of surface immunoglobulin on human B lymphocytes III. Physiological variations of sIg cells in peripheral blood. Clin Exp Immunol. 1978;33:441-452.[Medline]
52. Rheinberg A, Schuller E, Clench J, Smolensky MH. Recent Advances in the Chronobiology of Allergy and Immunology. New York: Pergamon Press; 1980;251.
53. Rheinberg A, Smolensky MH. Biological Rhythms Medicine. Cellular, Metabolic, Physiopathologic and Pharmacologic Aspects. Berlin and Heidelberg, Germany: Springer; 1983.
54. Gidlow DA, Church JF, Clayton BT. Haematological and biochemical parameters in an industrial workforce. Ann Clin Biochem. 1983;20:341-348.[Medline]
55. MacMurray JP, Barker JP, Armstrong JD, Bozzetti LP, Kuhn IN. Circannual changes in immune function. Life Sci. 1983;32:2363-2370.[Medline]
56. Johnson SA, Cambier JC. Ageing, autoimmunity and arthritis: senescence of the B cell compartment—implications for humoral immunity. Arthritis Res Ther. 2004;6:131-139.[Medline]
57. Allman D, Miller JP. B cell development and receptor diversity during ageing. Curr Opin Immunol. 2005;17:463-467.[Medline]
58. Frasca D, Riley RL, Blomberg BB. Humoral immune response and B-cell functions including immunoglobulin class switch are downregulated in aged mice and humans. Semin Immunol. 2005;17:378-384.[Medline]
59. Shi Y, Yamazaki T, Okubo Y, Uehara Y, Sugane K, Agematsu K. Regulation of aged humoral immune defense against pneumococcal bacteria by IgM memory B cell. J Immunol. 2005;175:3262-3267.[Abstract/Free Full Text]
60. Bernstein ED, Kaye D, Abrutyn E, Gross P, Dorfman M, Murasko DM. Immune response to influenza vaccination in a large healthy elderly population. Vaccine. 1999;17:82-94.[Medline]
61. Murasko DM, Bernstein ED, Gardner EM, et al. Role of humoral and cell-mediated immunity in protection from influenza disease after immunization of healthy elderly. Exp Gerontol. 2002;37:427-439.[Medline]
62. Kreft B, Fischer A, Kruger S, Sack K, Kirchner H, Rink L. The impaired immune response to diphtheria vaccination in elderly chronic hemodialysis patients is related to zinc deficiency. Biogerontology. 2000;1:61-66.[Medline]
63. Provinciali M, Montenovo A, Di Stefano G, et al. Effect of zinc or zinc plus arginine supplementation on antibody titre and lymphocyte subsets after influenza vaccination in elderly subjects: a randomized controlled trial. Age Ageing. 1998;27:715-722.[Abstract/Free Full Text]
64. Gardner EM, Bernstein ED, Popoff KA, Abrutyn E, Gross P, Murasko DM. Immune response to influenza vaccine in healthy elderly: lack of association with plasma ß-carotene, retinol, -tocopherol, or zinc. Mech Ageing Dev. 2000;117:29-45.[Medline]
65. Olsson J, Wikby A, Johansson B, Lofgren S, Nilsson BO, Ferguson FG. Age-related change in peripheral blood T-lymphocyte subpopulations and cytomegalovirus infection in the very old: the Swedish longitudinal OCTO immune study. Mech Ageing Dev. 2000;121:187-201.[Medline]
66. Huppert FA, Pinto EM, Morgan K, Brayne C. Survival in a population sample is predicted by proportions of lymphocyte subsets. Mech Ageing Dev. 2003;124:449-451.[Medline]
67. Kaplan J, Hess JW, Prasad AS. Impaired interleukin-2 production in the elderly: association with mild zinc deficiency. Trace Elements in Experimental Medicine. 1988;1:3-8.
68. Chandra RK. Effect of vitamin and trace element supplementation on immune responses and infection in elderly subjects. Lancet. 1992;340:1124-1127.[Medline]
69. Peretz A, Neve CJ, Siderova V, Fondu P. Effects of zinc supplementation on the phagocytic functions of polymorphonuclears in patients with inflammatory rheumatic diseases. J Trace Elem Electrolytes Health Dis. 1994;8:189-194.[Medline]

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