Antioxidant vitamins and human immune responses

Prevalence of Maternal Measles Antibody and Its Associated Factors among Infants in Coastal Karnataka, India

BACKGROUND

The current recommendation in India to commence first dose of measles immunization is at 9 months of age. The effectiveness of measles vaccination is greatly impacted by the level of maternal measles antibody (MMA) during infancy.

OBJECTIVES

To find the prevalence of MMA and to study the maternal and infant factors associated with persistence of MMA among the infants in a Indian rural community.

METHODOLOGY

Dried blood spot sample was collected before vaccination among infants aged 9 months and above when they came for first dose of measles vaccine to assess measles-specific maternal IgG antibody titers by enzyme immunoassay. Maternal and child factors influencing persistence of MMA were collected by interviewing the mothers. Association between various factors affecting seropositivity was tested using univariate logistic regression analysis and strength of association is reported as risk ratio with 95% confidence interval.

RESULTS

Based on the qualitative estimation among all the recruited children (250) in the study, 4 (1.6%) infants showed the presence of MMA whereas 25 (10%) of children had MMA on quantitative estimation. The effect of maternal factors, child nutrition, and sociodemographic factors on the presence of MMA was not found to be statistically significant.

CONCLUSION

The prevalence of persistent MMA (IgG titer ≥200 mIU/ml) among the infants aged 9-12 months was 10%. The choice of vaccinating infants at the end of 9 months for the first dose of measles vaccine is justified as the remaining (90%) of infants were susceptible for measles infection at this age.

Phytochemicals and antioxidative enzymes defence mechanism on occurrence of yellow vein mosaic disease of pumpkin (Cucurbita moschata)

Pumpkin (Cucurbita moschata) samples showing yellow vein mosaic disease in Varanasi region were identified with begomovirus infection using PCR amplification. A sequencing analysis of the full genome revealed that it is a strain of Tomato leaf curl Palampur virus (GenBank ID. FJ931537). Phytochemical composition and antioxidative enzyme levels were compared in infected and healthy plants. The study revealed that the amount of total protein declined in the infected leaves but elevated up to 135 % in the fruits of infected plants, whereas vitamin C and antioxidants declined in infected leaves as well as fruits. There was substantial increase in total phenol content in leaves (72 %) and fruits (300 %) of infected plants. In infected samples, substantial increase in activities of superoxide dismutases (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and catalase (CAT) was observed as compared to the uninfected control plants. The native PAGE showed alterations in the intensities of isozyme bands in the infected plants. The APX, GPX, CAT, SOD and glutamate dehydrogenase (GDH) bands were intense in the infected plants, whereas the GR isozyme showed reduced intensity in diseased plants.

Antibody response to hepatitis B vaccine in substance use disorder patients

The objectives of this study were to assess the prevalence of prognostic factors previously known to be associated with poor antibody response to hepatitis B vaccination in a sample of veterans presenting for substance use disorders treatment at a Veterans Health Administration (VA) Medical Center, assess vaccination response, and identify markers for poor response in this population. Results indicated that most participants had multiple prognostic factors previously known to be associated with poor antibody response including male gender, age over 40, smoking, and obesity. The rate of seroconversion in this sample was 51.9%. This is substantially lower than seen in healthy adults. Alcohol dependence was the only significant independent negative predictor of seroconversion in this sample. Substance use disorders treatment providers who are considering adding hepatitis B vaccination services to their clinics should be aware that the antibody response to the hepatitis B vaccination is inconsistent and that patients with particular demographic characteristics may be at heightened risk of poor antibody response.

Polyphenolics from various extracts/fractions of red onion (Allium cepa) peel with potent antioxidant and antimutagenic activities

In order to determine antioxidant activity, the five extracts/fractions of red onion peel were studied for their total content of phenolics (TPC), flavonoids (TFC), antioxidant activity (AOA), free radical scavenging activity (FRSA), assayed by DPPH radical in the terms of anti-radical power (ARP) and reducing power (RP), expressed as ascorbic acid equivalents (ASE)/ml. High TPC (384.7 +/- 5.0 mg GAE/g), TFC (165.2+/- 3.2 mg QE/g), AOA (97.4 +/- 7.6%), ARP (75.3 +/-4.5) and RP (1.6 +/-0.3 ASE/ml) were found for the ethyl acetate (EA) fraction. EA fraction had markedly higher antioxidant capacity than butylated hydroxytoluene (BHT) in preventive or scavenging capacities against FeCl3-induced lipid peroxidation, protein fragmentation, hydroxyl (site-specific and non-site-specific), superoxide anion and nitric oxide radicals. EA fraction also showed dose dependent antimutagenic activity by following the inhibition of tobacco-induced mutagenicity in Salmonella typhimurium strains (TA102) and hydroxyl radical-induced nicking in plasmid pUC18 DNA. HPLC and MS/MS analysis showed the presence of ferulic, gallic, protocatechuic acids, quercetin and kaempferol. The large amount of polyphenols contained in EA fraction may cause its strong antioxidant and antimutagenic properties. This information shows that EA fraction of red onion peel can be used as natural antioxidant in nutraceutical preparations.

ANTIOXIDANT EFFECTS OF TAURINE, VITAMIN C, AND VITAMIN E ON OXIDATIVE DAMAGE IN HIPPOCAMPUS CAUSED BY THE ADMINISTRATION OF 3-NITROPROPIONIC ACID IN RATS

The administration of 3-nitropropionic acid increases reactive oxygen species (ROS). Antioxidant defense mechanisms buffer these ROS converting them into non-damaging compounds. Taurine and vitamins C and E are antioxidants that play a role in the defense against cellular damage. This study examines the antioxidant effect of taurine, vitamin C, and vitamin E on acute hippocampal damage caused by 3-NP. Animals treated with 3-NP increased lipid peroxidation levels and astrocytic damage in the hippocampus. Administration of taurine, vitamin C, and vitamin E partially protected from oxidative damage, indicate that while all substances had antioxidant effects, only taurine showed morphological protection in surviving cells.

Restoration of the immune functions in aged mice by supplementation with a new herbal composition, HemoHIM

The effect of a new herbal composition, HemoHIM, on immune functions was examined in aged mice, in which various immune responses had been impaired. The composition HemoHIM was prepared by adding the ethanol-insoluble fraction to the total water extract of a mixture of three edible herbs, Angelica Radix, Cnidium Rhizoma and Paeonia Radix. Supplementation to the aged mice with HemoHIM restored the proliferative response and cytokine production of splenocytes with a response to ConA. Also, HemoHIM recovered the NK cell activity which had been impaired in the aged mice. Meanwhile aging is known to reduce the Th1-like function, but not the Th2-like function, resulting in a Th1/Th2 imbalance. HemoHIM restored the Th1/Th2 balance in the aged mice through enhanced IFN-gamma and IgG2a production, and conversely a reduced IL-4 and IgG1 production. It was found that one factor for the Th1/Th2 imbalance in the aged mice was a lower production of IL-12p70. However, HemoHIM restored the IL-12p70 production in the aged mice. These results suggested that HemoHIM was effective for the restoration of impaired immune functions of the aged mice and therefore could be a good recommendation for immune restoration in elderly humans.

Total phenol, antioxidant and free radical scavenging activities of some medicinal plants

Phenols, a major group of antioxidant phytochemicals, have profound importance due to their biological and free radical scavenging activities. To identify their potential sources, extracts of some plants were studied for their total phenolic content (TPC), antioxidant (AOA) and free radical scavenging activities (FRSA) by different methods at multiple concentrations followed by specific phenolic composition. The amount of TPC varied from 2.8 mg/g (Withania somnifera, roots) to 107.8 mg/g (Cassia fistula, fruits) and the AOA from 24.2% (Curcuma zeoderia, leaves) to 96.9% (Trewia nudiflora, leaves). Bark of Azadirachta indica, fruits of C. fistula, and leaves and fruits of T. nudiflora were found to have high TPC (89.8- 107.8 mg/g) and high AOA (84.8-96.9%). Promising plant parts were studied for their FRSA and reducing power (RP), where the bark of A. indica, Casuarina equisetifolia and Cinnamomum zeylanicum, flowers of Indigofera tinctoria, fruits of Lawsonia inermis, and fruits and leaves of T. nudiflora showed a very low inhibitory concentration value ranging from 0.14 to 0.26 mg/ml, efficiency concentration value from 6.1 to 11.6 mg/mg DPPH and reducing power value from 0.6 to 2.8 ascorbic acid equivalents (ASE/ml), and reasonably high values (8.5 -16.2) of anti-radical power (ARP), indicating their strong FRSA. They also showed better inhibition of hydroxyl radical induced deoxyribose degradation than that of reference standard. Fruits of C. fistula with high phenols (107.8 mg/g) showed poor reducing power (5.9 ASE/ml) and ARP (4.7); in contrast, the bark of C. equisetifolia and fruits of L. inermis were with comparatively lower phenols (72.1 and 75.8 mg/g) but exhibited good ARP (16.2 and 14.4) and reducing power (0.7 and 0.6 ASE/ ml, respectively). Some of the plants were also found effective in protecting plasmid DNA nicking induced by hydroxyl radicals generated by Fenton's reaction. They were further assayed for their specific phenolic composition through high-performance liquid chromatography and MS/MS, where the amount of caffeic acid varied from 0.312 to 0.797 mg/g, chlorogenic acid from 0.018 to 2.109 mg/g, ellagic acid from 0.009 to 0.902 mg/g, ferulic acid from 0.036 to 0.078 mg/g, gallic acid from 0.192 to 3.597 mg/g, kaempferol from 0.011 to 0.910 mg/g, quercetin from 0.047 to 1.106 mg/g and rutin from 0.059 to 2.029 mg/g.

Effect of multivitamins in an effervescent preparation on the respiratory burst of peritoneal macrophages in mice

The effect of regular intake of low doses of an effervescent multivitamin preparation on the free-radical-producing activity of murine peritoneal macrophages under conditions resembling a possible infection was studiedin vitro. Initially, several groups of mice were fed a basal diet and given, for 2 weeks, water without or with supplementation of either α -tocopherol, ascorbic acid, riboflavin or a multivitamin preparation. The supplementation period was followed by a 2-week wash-out time interval during which control and multivitamin groups received deionized water. Macrophage stimulation tests using chemiluminescent spectroscopy were performed at the end of the supplementation and wash-out periods to determine cell counts and their capacity to produce free radicals. Multivitamin supplementation increased the number, and the reactive oxygen species-producing activity, of macrophages. This effect persisted for 2 weeks after higher doses of supplementation were stopped. Multivitamin supplementation lowered the steady-state free radical concentrations of liver and spleen as measured by electron paramagnetic resonance spectroscopy. It also increased the antioxidant reactivity of the same organs, while there was no effect on the free radical concentration and antioxidant capacity of the kidney and brain. When taken regularly, low doses of multivitamin supplementation may have a beneficial effect on the defence mechanisms of the organism.

Occurrence of yellow mosaic geminiviral disease on bitter gourd (Momordica charantia) and its impact on phytochemical contents

Natural occurrence of yellow mosaic disease was observed on bitter gourd (Momordica charantia). Association of geminivirus with the disease was investigated through polymerase chain reaction using geminivirus-specific primers and Southern hybridization with a probe prepared from the cloned DNA of a known geminivirus. The fruits, leaves and stem of infected and healthy plants were studied for phytochemical composition. The amounts of protein were 49%, 50% and 66% higher, total carotenoids were 36%, 33% and 40% lower, vitamin C were 23%, 48% and 50% lower, total phenols were 28%, 31% and 43% lower, and antioxidant activity were 36%, 48% and 43% lower in the severely virus infected fruits, leaves and stem, respectively, as compared with healthy plants. The loss in the quantity of these phytochemicals was also observed even in mild infected plants, which further increased with the severity of the symptoms. Similarly, ethanol and 50% ethanol soluble extractive were also 25-43% lower in the fruits, leaves and stem of infected plants as compared with the healthy plants. A 45% and 54% lower caffeic acid, and 78% and 59% lower amounts of ferulic acid in the fruits and stem, respectively, and a 25% loss of gallic acid were noticed in the leaves of the severely infected plants.

The effect of vitamin E supplementation on antioxidant enzyme activities and lipid peroxidation levels in hemodialysis patients

BACKGROUND

This study has been undertaken to investigate the possible alterations of oxidant/antioxidant status in uremic patients undergoing hemodialysis (HD) and the effects of vitamin E supplementation.

METHODS

Erythrocyte antioxidant enzyme activities [glutathione peroxidase (GSHPx), superoxide dismutase (SOD) and catalase (CAT)] and thiobarbituric acid reactive substance (TBARS) concentrations as a measure of lipid peroxidation in HD patients have been determined and compared with healthy controls. The patient group consisted of 36 uremic patients 21-75 years of age undergoing maintenance HD three times weekly for an average of 41 months. The efficiency of Vitamin E therapy in dialysis patients was also assessed by re-evaluating antioxidant status of the same patients after supplementation of the vitamin E in a dosage of 600 mg/daily for 14 weeks.

RESULTS

A significant decrease in the activities of erythrocyte SOD, CAT and GSHPx and a significant increase in TBARS concentrations were found in patient group compared to control group (p<0.001). A significant correlation between GSHPx activities and duration of HD therapy was also observed (r=-0.46, p<0.01). Vitamin E supplementation caused an increase in GSHPx and SOD activities and a decrease in TBARS concentrations. A slight but not significant increase in CAT activity was also observed by Vitamin E.

CONCLUSIONS

The results suggest the presence of an oxidative activity and the possible preventive role of Vitamin E therapy in uremic patients undergoing HD.

Selenium deficiency and viral infection

The discovery that the juvenile cardiomyopathy known as Keshan disease likely has a dual etiology that involves both a nutritional deficiency of the essential trace mineral selenium (Se) as well as an infection with an enterovirus provided the impetus for additional studies of relationships between nutrition and viral infection. An amyocarditic strain of coxsackievirus B3, CVB3/0, converted to virulence when it was inoculated into Se-deficient mice. This conversion was accompanied by changes in the genetic structure of the virus so that its genome closely resembled that of other known virulent CVB3 strains. Similar alterations in virulence and genomic composition of CVB3/0 could be observed in mice fed normal diets but genetically deprived of the antioxidant selenoenzyme glutathione peroxidase (knockout mice). More recent research has shown that a mild strain of influenza virus, influenza A/Bangkok/1/79, also exhibits increased virulence when given to Se-deficient mice. This increased virulence is accompanied by multiple changes in the viral genome in a segment previously thought to be relatively stable. Epidemic neuropathy in Cuba has features that suggest a combined nutritional/viral etiology. Further research, both basic and applied, is needed to assess properly the possible role of malnutrition in contributing to the emergence of novel viral diseases.

Changes in the ascorbic acid levels of peritoneal lymphocytes and macrophages of mice with endotoxin-induced oxidative stress

Ascorbic acid (AA) is an important cytoplasmic antioxidant that mice synthesize in the liver, the intracellular levels of which decrease in an oxidative stress situation such as endotoxic shock. The present work deals with the changes in AA levels, that modulate the immune function, in the two main immune cells, namely macrophages and lymphocytes, from female BALB/c mice suffering endotoxic shock caused by intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS) (100 mg/kg). The intake by cells of this antioxidant present in vitro at different concentrations was also studied. The animals show an oxidative stress, standardized in previous studies, that causes mortality at 30 h after LPS injection. The cells were obtained from the peritoneum at 2, 4, 12 and 24 h after LPS or PBS (control) injections and were incubated without or with AA at 0.01, 0.1 and 1 mM for 10, 30, 60, 120 or 180 min. The hepatic AA levels were also studied at 0, 2, 4, 12 and 24 h after LPS injection. The peritoneal cells obtained from animals injected with LPS showed increased AA levels in relation to the control cells at all times after LPS injection, with maximal effect at 12h. The AA levels decreased after this time, in agreement with changes in the AA hepatic levels. The increase was due to the AA of lymphocytes since macrophages showed a decrease in AA at different times after LPS injection. Both cells showed an increase in the intracellular levels of AA when this antioxidant was added in vitro. This takes place mainly at 30-60 min of incubation in cells from controls and at 10 min in cells from treated mice 12-24 h after LPS injection. The incorporation decreased at these times of endotoxic shock, a few hours before death. In all cases AA levels were higher in lymphocytes than in macrophages, and 1 mM was the most effective concentration. These results suggest that the immune cells need appropriate levels of antioxidants, such as AA, under oxidative stress conditions, and that while lymphocytes take and accumulate AA, macrophages use it.

Antioxidants and viral infections: host immune response and viral pathogenicity

Malnutrition has long been associated with increased susceptibility to infectious disease. The increase in severity from and susceptibility to infectious disease in malnourished hosts is thought to be the result of an impaired immune response. For example, malnutrition could influence the immune response by inducing a less effective ability to manage the challenge of an infectious disease. Work in our laboratory has demonstrated that not only is the host affected by the nutritional deficiency, but the invading pathogen is as well. Using a deficiency in selenium (Se) as a model system, mice deficient in Se were more susceptible to infection with coxsackievirus, as well as with influenza virus. Se-deficient mice develop myocarditis when infected with a normally benign strain of coxsackievirus. They also develop severe pneumonitis when infected with a mild strain of influenza virus. The immune system was altered in the Se-deficient animals, as was the viral pathogen itself. Sequencing of viral isolates recovered from Se-deficient mice demonstrated mutations in the viral genome of both coxsackievirus and influenza virus. These changes in the viral genome are associated with the increased pathogenesis of the virus. The antioxidant selenoenzyme, glutathione peroxidase-1, was found to be critically important, as glutathione peroxidase knockout mice developed myocarditis, similar to the Se-deficient mice, when infected with the benign strain of myocarditis. This work points to the importance of host nutrition in not only optimizing the host immune response, but also in preventing viral mutations which could increase the viral pathogenicity.

Low carotenoid concentration and the risk of HIV seroconversion in Pune, India

Low vitamin A and carotenoid levels could increase the risk of sexual HIV acquisition by altering the integrity of the genital epithelium or by immunologic dysfunction. We addressed this issue by measuring serum vitamin A and carotenoid levels in patients who were at risk of subsequent HIV infection. In a nested case-control study in individuals attending two sexually transmitted disease (STD) clinics in Pune, India, serum micronutrient levels were measured in 44 cases with documented HIV seroconversion (11 women and 33 men) and in STD patients matched for gender and length of follow-up with no subsequent HIV seroconversion (controls). STD patients in Pune had low vitamin A and carotenoid levels, and low serum beta-carotene levels were independently associated with an increased risk of subsequent HIV seroconversion. STD patients with beta-carotene levels less than 0.075 micromol/L were 21 times more likely to acquire HIV infection than those with higher levels (adjusted odds ratio = 21.1; p =.01). No such association was observed in case of other non-provitamin A carotenoids. This study reports the first evidence of an association between low serum provitamin A carotenoid levels and an increased risk for heterosexual HIV acquisition in STD patients in Pune, India.

Immunological restoration and anti-tumor effect by Japanese herbal medicine in aged mice

We examined the effect of two Japanese herbal medicines (Kampo-Hozai) on immunological functions and anti-tumor activity in old mice. Hochu-ekki-to (TJ-41) was remarkably effective in the restoration of impaired immune functions of old mice, in terms of number of T cells and NK cells, and anti-SRBC antibody response, while it was not effective in enhancing immune functions of young mice. Juzen-taiho-to was also effective in increasing the number of T cells, remarkably, and NK cells, slightly, in the aged mice. While a significant increase was not observed in young mice. NK activity increased both in young and old mice with the treatment of TJ-48. A significant decrease was observed in metastatic pulmonary colonies of B16 melanoma cells both in young and old mice treated with Juzen-taiho-to for 16 weeks. These results suggested that some of Japanese herbal medicines were useful in restoration of impaired immune functions of old mice and could be recommended for human elderly.

Antitumor activity of astaxanthin and its mode of action

Astaxanthin, a carotenoid without vitamin A activity, may exert antitumor activity through the enhancement of immune responses. Here, we determined the effects of dietary astaxanthin on tumor growth and tumor immunity against transplantable methylcholanthrene-induced fibrosarcoma (Meth-A tumor) cells. These tumor cells express a tumor antigen that induces T cell-mediated immune responses in syngenic mice. BALB/c mice were fed astaxanthin (0.02%, 40 micrograms/kg body wt/day in a beadlet form) mixed in a chemically defined diet starting zero, one, and three weeks before subcutaneous inoculation with tumor cells (3 x 10(5) cells, 2 times the minimal tumorigenic dose). Three weeks after inoculation, tumor size and weight were determined. We also determined cytotoxic T lymphocyte (CTL) activity and interferon-gamma (IFN-gamma) production by tumor-draining lymph node (TDLN) and spleen cells by restimulating cells with Meth-A tumor cells in culture. The astaxanthin-fed mice had significantly lower tumor size and weight than controls when supplementation was started one and three weeks before tumor inoculation. This antitumor activity was paralleled with higher CTL activity and IFN-gamma production by TDLN and spleen cells in the astaxanthin-fed mice. CTL activity by TDLN cells was highest in mice fed astaxanthin for three weeks before inoculation. When the astaxanthin-supplemented diet was started at the same time as tumor inoculation, none of these parameters were altered by dietary astaxanthin, except IFN-gamma production by spleen cells. Total serum astaxanthin concentrations were approximately 1.2 mumol/l when mice were fed astaxanthin (0.02%) for four weeks and appeared to increase in correlation with the length of astaxanthin supplementation. Our results indicate that dietary astaxanthin suppressed Meth-A tumor cell growth and stimulated immunity against Meth-A tumor antigen.

Chromatographic determination of carotenoids in foods

In recent years, there has been particular emphasis on obtaining more accurate data on the types and concentrations of carotenoids in foods for various health and nutrition activities. The analysis of carotenoids is complicated because of the diversity and the presence of cis-trans isomeric forms of this group of compounds. In addition, a wide variety of food products of vegetal and animal origin, vegetables and animal samples contain carotenoids, and a great range of carotenoids can be found in these samples. The characteristic conjugated double bond system of carotenoids produces the main problem associated with work and manipulation on carotenoids, that is their particular instability, especially towards light, heat, oxygen and acids. For this reason, several precautions are necessary when handling carotenoids. Another problem associated with analysis of carotenoids is the difficulty in obtaining standard compounds. High-performance liquid chromatographic methods for the determination of carotenoids in foods are reviewed. The sample extraction and treatment, carotenoid purification and standard manipulation are briefly commented on. We present a critical assessment of chromatographic methods developed for the determination of carotenoids in foods. Finally, some methods for carotenoid ester separation are reviewed.

Vitamin E enhances the immune functions of young but not old mice under restraint stress

Young and old C57BL/6 male mice were given a diet containing a high dose of vitamin E (VE treatment) and its effect on the immune system was examined before and after the exposure to restraint stress. The VE treatment per se gave rise to a slight increase of splenic T cells in percentage and a significant enhancement of Con A response of spleen cells in young, but not in old mice. The VE treatment also resulted in the enhancement of production of IL-2 and IFNgamma in young, but not in old mice. Restraint stress led to thymic involution in both young and old mice. This thymic involution was not ameliorated by the VE treatment. Percentage of splenic T cells and their mitogenic response decreased just after the stress, but soon rebounded over the control level. The VE treatment further enhanced the recovery after the stress in young mice, but on the contrary suppressed the recovery in old mice. The results in the present study suggested that the VE treatment was effective in the prevention of immunological decline of young mice before and after the exposure to the stress. On the other hand, such a preventive effect was not observed in old mice that were already in the depressed state of immunological functions.

Modulation of human T-lymphocyte functions by the consumption of carotenoid-rich vegetables

A human intervention study was conducted to determine the effect of the consumption of carotenoid-rich vegetables on the immune system. Subjects, (twenty-three men), who were non-smokers, were not restricted in their daily diet, except that they had to abstain from fruit and vegetables high in carotenoids throughout the whole study period. The study was divided into four periods, each lasting 2 weeks: weeks 1-2: low-carotenoid period; throughout weeks 3-8: daily consumption of 330 ml tomato juice (40 mg lycopene/d, 1.5 mg beta-carotene/d) (weeks 3-4), 330 ml carrot juice (21.6 mg beta-carotene/d, 15.7 mg alpha-carotene/d, 0.5 mg lutein/d) (weeks 5-6), 10 g dried spinach powder (11.3 mg lutein/d, 3.1 mg beta-carotene/d) (weeks 7-8). Blood was collected weekly from subjects after a 12 h fast. T-lymphocyte functions were assessed by measuring proliferation and secretion of immunoreactive cytokines. The consumption of a low-carotenoid diet resulted in a significantly reduced proliferation of peripheral blood mononuclear cells (PBMC) cultured with concanavalin A. After 2 weeks of tomato juice consumption and until the end of the intervention period lymphocyte proliferation was not significantly changed compared with proliferation at the end of the depletion period. Secretion of cytokines by T-helper-1-like lymphocytes (interleukin (IL)-2) and by T-helper-2-like lymphocytes (IL-4) was influenced by the dietary intervention. IL-2 and IL-4 secretion values were significantly suppressed after the low-carotenoid diet (P < 0.001 and P < 0.05 respectively compared with baseline). Tomato juice consumption significantly enhanced IL-2 (P < 0.001) and IL-4 secretion (P < 0.05) compared with the end of depletion period. After carrot juice and spinach powder consumption the cytokine secretion capacity of PBMC was not significantly different from that at the end of the depletion period. In conclusion, the results of the present study indicate that a low-carotenoid diet reduces T-lymphocyte functions and addition of tomato juice restores these functions. This modulation could not be explained by changes in the plasma carotenoid concentrations. The active constituents in tomato juice as well as the biological significance of this immunomodulation remain to be determined.

Effects in vitro of several antioxidants on the natural killer function of aging mice

The aim of the present work is to study the change with aging in the effect in vitro of several antioxidants: thiazolidine-4-carboxylic acid or thioproline, N-acetylcysteine (NAC), ascorbic acid (AA), and alpha-tocopherol (vitamin E, VE) on the natural killer (NK) activity in mononuclear cells from axillary nodes, spleen, thymus and peritoneal leukocytes from BALB/c male mice. Young (8+/-2 weeks), adult (24+/-2 weeks). mature (48+/-2 weeks), and old (72+/-2 weeks) animals were studied. A nonradioactive cytotoxic assay with cells from the murine lymphoma YAC-1 as target cells and a relation effector cells/target cells of 10/1 were used. The concentrations of the different antioxidants were: 1 mM for thioproline and N-acetylcysteine and 5 microM for ascorbic acid and alpha-tocopherol, which induced a maximum effect in our previous dose-response experiments. The results show that, in general, the above antioxidants cause an enhancement of the NK activity at all ages studied, this stimulation being higher with thioproline and N-acetylcysteine than with ascorbic acid and alpha-tocopherol. The effects were similar for the three lymphoid organs and the peritoneum. This stimulation of the NK activity by antioxidants is an important favorable response, especially in old mice, in which age results in a decrease in NK function and, therefore, in a higher incidence of neoplasia.

Effects of carotenoids on human immune function

Many epidemiological studies have shown an association between diets rich in carotenoids and a reduced incidence of many forms of cancer, and it has been suggested that the antioxidant properties of these compounds are a causative factor. Attention has focused on the potential role of one specific carotenoid, beta-carotene, in preventing cancer, and numerous publications have described in vitro experiments and animal studies which suggest that not only can this carotenoid protect against the development of cancer, but also several other chronic diseases. Since the immune system plays a major role in cancer prevention, it has been suggested that beta-carotene may enhance immune cell function. Several human trials, using dietary beta-carotene supplementation with a wide range of intakes, have been undertaken to address this hypothesis. The general conclusion of these studies is that this compound can enhance cell-mediated immune responses, particularly in the elderly. The present article will review some of these human studies and, hopefully, complement the reviews of other authors associated with the present symposium, some of whom will also describe work in this area. Potential mechanisms for the effects of carotenoids on immune function will also be reviewed. Finally, possible reasons for the failure of three major prospective studies to demonstrate a beneficial effect of beta-carotene supplementation on lung cancer risk will be discussed.

Effects of dietary antioxidants on the immune function of middle-aged adults

The immune system is highly reliant on accurate cell-cell communication for optimal function, and any damage to the signalling systems involved will result in an impaired immune responsiveness. Oxidant-mediated tissue injury is a particular hazard to the immune system, since phagocytic cells produce reactive oxygen species as part of the body's defence against infection. Adequate amounts of neutralizing antioxidants are required, therefore, to prevent damage to the immune cells themselves. Many antioxidants can be obtained directly from the diet (e.g. ascorbic acid, alpha-tocopherol, carotenoids and polyphenolic flavonoids) or require micronutrients as integral components (e.g. Se in the metalloenzyme glutathione peroxidase (EC 1.11.1.9)). Numerous epidemiological studies have found strong associations between diets rich in antioxidant nutrients and a reduced incidence of cancer, and it has been suggested that a boost to the body's immune system by antioxidants might, at least in part, account for this. Although more striking effects have been observed in the elderly, there is also evidence that antioxidant nutrients can modify cell-mediated immune responses in younger individuals. Indeed, it might be essential to have an adequate intake of antioxidant nutrients from an early age in order to help prevent the development of, or at least delay the onset of, several degenerative disorders. The present paper will review the effects of specific nutrients on immune function in young to middle-aged human subjects, focusing on the antioxidant vitamins C and E, and on Se. A further review, dealing more specifically with the effects of carotenoids on human immune function, will be presented at a forthcoming meeting of the Nutrition Society.

Variability of oxygen radical absorbance capacity (ORAC) in different animal species

The oxygen radical absorbance capacity (ORAC) was measured both in whole (ORAC-T) and deproteinized (ORAC-AS) plasma samples of human, pig, cow, rabbit, dog, cat, sheep, horse, dolphin, turkey, guinea-hen and chicken. In the 12 species, ORAC-T data, expressed as micromoles of peroxyl radicals trapped by 11 of sample, were found scattered between 8,600 and 23,000 micromol/l. The species with the highest ORAC-T values were cat among mammals and chicken among avies. ORAC-AS values ranged between 600 and 2000 micromol/l, with the highest values found in dolphin and sheep among mammals, while chicken was first among avies. In the 12 species, the relative contribution of ORAC-AS in relation to ORAC-T ranged from 5% to 20%. Protein SH-groups and uric acid were measured in plasma of all species, but no significant correlation was found between thiols and ORAC-T values or between uric acid and ORAC-AS values. Our results show that: (1) the ORAC method is reproducible and sensitive enough to be used in the comparison of the peroxyl-radical absorbance capacity of protein and non-protein plasma components in different animal species; (2) both in mammals and in avies, there is a deep intra-class heterogeneity of ORAC-T and ORAC-AS values; (3) by considering most species, plasma proteins and lipoproteins account for about 85-90% of the overall peroxyl-radical trapping capacity. In the dolphin only, the protein contribution decreases to 80%; (4) uric acid accounts for about one-half of the ORAC-AS value in human, guinea-hen and for about one-third in chicken, while it provides a very limited contribution in other species. We conclude that species with the highest ORAC-T, like cat and chicken, or with the highest ORAC-AS, like dolphin, are interesting models to study the reasons of such a marked antioxidant defense in the plasma.

On the adaptive significance of stress-induced immunosuppression

We approach the field of stress immunology from an ecological point of view and ask: why should a heavy physical workload, for example as a result of a high reproductive effort, compromise immune function? We argue that immunosuppression by neuroendocrine mechanisms, such as stress hormones, during heavy physical workload is adaptive, and consider two different ultimate explanations of such immunosuppression. First, several authors have suggested that the immune system is suppressed to reallocate resources to other metabolic demands. In our view, this hypothesis assumes that considerable amounts of energy or nutrients can be saved by suppressing the immune system; however, this assumption requires further investigation. Second, we suggest an alternative explanation based on the idea that the immune system is tightly regulated by neuroendocrine mechanisms to avoid hyperactivation and ensuing autoimmune responses. We hypothesize that the risk of autoimmune responses increases during heavy physical workload and that the immune system is suppressed to counteract this.

Dietary oxidative stress and the potentiation of viral infection

Oxidative stress is implicated in the pathogenesis of several viral infections, including hepatitis, influenza, and AIDS. Dietary oxidative stress due to either selenium or vitamin E deficiency increases cardiac damage in mice infected with a myocarditic strain of coxsackievirus B3. Such dietary oxidative stress also allows a normally benign (i.e., amyocarditic) coxsackievirus B3 to convert to virulence and cause heart damage. This conversion to virulence is due to a nucleotide sequence change in the genome of the benign virus, which then resembles more closely the nucleotide sequence of virulent strains. Although it has been known for many years that poor nutrition can affect host response to infection, this is the first report of host nutrition affecting the genetic sequence of a pathogen. Further research is needed to determine whether poor host nutrition plays any role in the emergence of new viral diseases via alterations in he genotype of an infectious agent.

Reversing and restoring immune functions

Restoration of immunological functions is keenly needed for the improvement of quality of life of the elderly as the elderly population is rapidly increasing throughout the world. A brief review was made on the methods to restore or reverse immunological functions in the aged human and animals, including those presented in the Mini-Symposium at the 1st International Conference on Immunology and Aging. The methods discussed were (1) grafting of cells and tissues, (2) dietary manipulation, (3) free radical scavengers or anti-oxidants, (4) thymic peptides, (5) endocrine manipulation and (6) physical exercise. There is no easy and simple method for immunological restoration, as people are variable in terms of genetics, habit and culture. We need comprehensive study to test the effect of combination of a few or several methods for immunological restoration.