I. Depressed immunological function in zinc-deprived rats as measured by mitogen response of spleen, thymus, and peripheral blood

Mitogen-Induced Interferon Gamma Production in Human Whole Blood: The Effect of Heat and Cations

BACKGROUND

Interferon-gamma release assays (IGRAs) are blood tests used to measure the amount of interferon-γ (IFN-γ) released by T lymphocytes after stimulation by antigens specific for the diagnosis of latent tuberculosis infection. A mitogen serves as a positive control to assess the immune function in IGRAs.

METHODS

This in vitro study was conducted to evaluate IFN-γ production by human whole blood stimulated with heat-treated and/or cation-supplemented phytohemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM), using QuantiFERON-TB Gold Kit ELISA tests.

RESULTS

The optimal concentrations of PWM, Con A and PHA for IGRAs were 2 µg/mL, 5 µg/mL and 10 µg/mL, respectively. The results showed that IFN-γ production in response to PWM was the highest and PHA was the lowest amount. The median values of three mitogens were in the following order: PWM≥Con A≥ positive control>>PHA-P>>negative control. PWM and PHA were heat stable, while Con A was heat sensitive. The mitogen response of lymphocytes to untreated or heat-treated PWM and heat-treated Con A was increased in 1 mM Ca2+-supplemented groups, whereas the response to heat-treated PHA was decreased. Exposure to 1 mM Mg2+ had no effect on untreated or heat-treated PWM, and a concentration of 1 mM Zn2+ inhibited the stimulation of un-treated PWM. We found that calcium supplementation improved the PWM-induced production of IFN-γ.

CONCLUSION

Therefore, PWM is an appropriate mitogen for use as a positive control in IGRAs. It is a potential indicator of cytokine production in the diagnostic as well as research settings, and calcium supplementation improved stimulation.

Iron and zinc exploitation during bacterial pathogenesis

Ancient bacteria originated from metal-rich environments. Billions of years of evolution directed these tiny single cell creatures to exploit the versatile properties of metals in catalyzing chemical reactions and biological responses. The result is an entire metallome of proteins that use metal co-factors to facilitate key cellular process that range from the production of energy to the replication of DNA. Two key metals in this regard are iron and zinc, both abundant on Earth but not readily accessible in a human host. Instead, pathogenic bacteria must employ clever ways to acquire these metals. In this review we describe the many elegant ways these bacteria mine, regulate, and craft the use of two key metals (iron and zinc) to build a virulence arsenal that challenges even the most sophisticated immune response.

Trace elements and immune responses

The common association of malnutrition and infection has led to many studies that have examined the effects of nutritional status on immunocompetence. Children with the syndromes of marasmus and kwaskiorkor show marked impairment of cell-mediated immunity (CMI), complement system, microbicidal function of polymorphonuclear leukocytes (PMN), and secretory IgA antibody response. The extensive literature on this burgeoning field has been summarized(1-5,40) Clinical malnutrition, however, is a complex combination of the deficiencies of many nutrients, including proteins, lipids, carbohydrates, vitamins, macrominerals and trace elements. Thus it is of fundamental importance to examine the influence of individual dietary factors on immune responses and disease (Fig. 1). Here Ranjit Chandra discusses the role of trace elements in host resistance to infection and other pathological diseases.

Influence of Stress and Nutrition on Cattle Immunity

Today, the scientific community readily embraces the fact that stress and nutrition impact every physiologic process in the body. At last, the specific mechanisms by which stress and nutrition affect the immune function are being elucidated. The debate among animal scientists concerning the definition and quantification of stress as it relates to animal productivity and well-being is ongoing. However, an increased appreciation and understanding of the effects of stress on livestock production has emerged throughout the scientific community and with livestock producers. The intent of this article is to provide an overview of the general concepts of stress and immunology, and to review the effects of stress and nutrition on the immune system of cattle.

Trace metals and the elderly

The elderly are at nutritional risk as a result of multiple physiological, social, psychological, and economic factors. Elderly persons have a higher incidence of chronic diseases and associated intake of medications that may affect nutrient utilization. Social and economic conditions can adversely affect dietary choices and eating patterns. Physiological functions naturally decline with age, which may influence absorption and metabolism. Loneliness and reluctance to eat may complicate an already marginal situation. This article reviews specific trace metals in relation to the elderly. Our objectives are to provide Dietary Reference Intakes for older adults, to provide information on presenting features and functional consequences of trace metal deficiency, and to discuss potential effects and/or benefits of trace metal supplementation in the elderly.

Correction of hypozincemia following liver transplantation in children is associated with reduced urinary zinc loss

Zinc deficiency is a relatively common problem in children with chronic liver disease. We have previously shown inappropriate urinary zinc excretion in children with chronic liver disease and hypozincemia. This study was designed to determine if zinc deficiency and inappropriate urinary zinc losses are corrected in children with liver disease by liver transplantation. Thirty-three patients (age 1-19 years) underwent 35 liver transplants for acute and chronic liver disease. At the time of transplant, 17 patients had low plasma zinc (hypozincemic) (plasma zinc, 45.4 +/- 1.8 microg/dL), whereas 18 had normal plasma zinc (75.7 +/- 3.8). Before transplant, patients with zinc deficiency had higher urinary zinc to creatinine ratio compared with those with normal zinc status (6.6 +/- 1.9 vs. 2.2 +/- 0.6; P =.03) and lower serum albumin concentrations (low: 2.8 +/- 0.1 vs. normal: 3.3 +/- 0.2; P =.02). After transplant, there was a significant reduction in urinary zinc losses in the hypozincemic group followed by normalization of plasma zinc levels by 7 days posttransplant. These data suggest that the abnormal renal zinc homeostasis that is present in approximately 50% of pediatric patients undergoing liver transplant is rapidly improved and biochemical zinc deficiency is reversed after liver transplantation.

Functional capacity of the residual lymphocytes from zinc-deficient adult mice

Zn deficiency has been shown to reduce host defence drastically. It was of interest to determine the capacity of the residual lymphocytes from Zn-deficient mice to proliferate and produce lymphokines in response to stimulation since there are many Zn-dependent metalloenzymes that might be altered by the deficiency. To address this question, young adult A/J mice were provided Zn-deficient or Zn-adequate diets or restricted amounts of a Zn-adequate diet for 30 d. Splenocytes from moderately or severely Zn-deficient adult A/J mice gave normal proliferative responses and generated adequate interleukin II (IL-2) activity when stimulated with the mitogen Concanavalin A. However, splenocytes from deficient mice exhibited a higher degree of proliferation (about 150%) and production of IL-2 in response to foreign target cells compared with T-cells prepared from mice provided a Zn-adequate diet. B-cells from deficient mice stimulated in vivo with sheep erythrocytes produced fewer total numbers of plaque-forming cells (PFC) per spleen. Nevertheless, the proportion or number of PFC/10(6) viable splenocytes and the amounts of IgM and IgG antibody produced per PFC were equivalent to those of adequately-fed and restricted-fed controls. The previously described responses were not significantly affected by whether the level of Zn in the culture medium was adequate or limiting. Based on these tests it appeared that the residual splenic lymphocytes of Zn-deficient mice were able to carry out many fundamental immune processes.

Progeny performance when dams and chicks are fed supplemental zinc

Three consecutive trials involving approximately 700 to 800 broilers (0 to 28 days) were conducted to examine effects on growth and immunity of chicks after supplementing dams with inorganic Zn versus organic Zn. Offspring from hens fed a basal diet (72 mg Zn/kg) or diets with 152 mg Zn/kg supplemented with ZnO or organic Zn-Met were randomized across four battery brooders. Chicks were fed a starter diet without supplemental Zn containing 100 mg Zn/kg or diets supplemented with 40 mg/kg Zn from ZnO and DL-Met or Zn-Met containing 140 mg Zn/kg. No differences among treatments (P greater than .05) were found in feed conversion or average BW. Supplemental Zn-Met in hen diet increased (P less than .06) cellular immune response in progeny. Embryonic bone weights were higher (P less than .05) in progeny when dams were fed Zn-Met. Zinc as Zn-Met in diets of dams and progeny enhanced primary antibody titers to Salmonella pullorum antigen.

The interaction of burn injury and zinc nutriture as assessed by the humoral response to sheep red blood cells in a burn rat model

Clinical and animal studies suggest that burn injury induces alterations in zinc metabolism. It also has been established that zinc nutriture can cause alterations in the immune response, but there is a paucity of information concerning the interrelationship between burn injury, zinc nutriture and the immune response. In the present study, rats were subjected to full skin thickness dorsal scald injuries covering 30 per cent of the total body surface and then maintained on sufficient or deficient zinc intake. The rats were immunized with sheep red blood cells (SRBC) on day 6 postburn and killed 4 days later. The spleens were excised and spleen lymphocytes isolated and used in a Jerne plaque assay to determine the number of plaque-forming cells (PFC). The burn/zinc-sufficient regimen significantly increased (P less than 0.01) the PFC response when compared to unburned zinc-sufficient or zinc-deficient control rats. Burned rats that were maintained on a zinc-deficient regimen showed a significant decrease (P less than 0.05) in PFC when compared to burned rats maintained on a zinc-sufficient regimen. This study indicates an interaction of zinc in the primary humoral immune response following thermal injury.

Immunological aspects of toxicology: premises not promises

The immune system is gaining increasing attention as a target of toxicant action. Many compounds, including metals, drugs, and pesticides, are able to alter immune functions. Additionally, the ability of toxicants to experimentally alter resistance to a variety of bacterial, viral, and tumor challenges is suggestive for the possible involvement of toxicants in morbidity and mortality. However, the implications of immunotoxicology as a subject of study may not be fully realized in some laboratories due to unfamiliarities into the workings of immunity by toxicologists. In an attempt to bridge this toxicology-immunology gap, this paper presents the major concepts of the immune system by reviewing specific examples of immune responses and their environmental interactions. Data from selected toxins are then used to illustrate how these responses may be altered.

Effect of nutritional zinc-deficiency on O6-alkylguanine-DNA-methyl-transferase activities in rat tissues

The effect of nutritional zinc-deficiency on the activities of O6-alkylguanine:DNA methyltransferase (AGT) in 9 rat tissues including liver, lung, kidney, spleen, brain, esophagus, forestomach, gastric-stomach and small intestine has been examined. Individual tissue extracts prepared from zinc-deficient and pair-fed, zinc-sufficient rats were incubated with N-[3H]methylnitrosourea-methylated calf thymus DNA for 1 h. The activities of AGT in these tissues were measured by two methods: (a) the transfer of the methyl group from O6-methylguanine in substrate DNA to AGT protein, and (b) the determination of the ratio of O6-methylguanine:7-methylguanine remaining in substrate DNA following incubation. AGT activities (expressed as fmol protein methylated/h per mg protein) were significantly reduced in the esophagus, spleen and lungs of zinc-deficient rats as compared to those in their corresponding zinc-sufficient counterparts. The ratio of O6-methylguanine:7-methylguanine was also reduced in the esophagus of the zinc-deficient rat. These results were consistent with our earlier findings that dietary zinc-deficiency enhances nitrosamine-induced esophageal carcinogenesis in rats.

The effect of dietary zinc and prothymosin alpha on cellular immune responses of RF/J mice

Mice of the RF/J strain on a normal diet are defective in some aspects of cellular immunity, as evidenced by their susceptibility to infection with Candida albicans, their failure to release detectable quantities of circulating migration inhibitory factor (MIF) in vivo, and the presence of a low rate of phagocytosis and killing by peritoneal macrophages. When the mice were fed a high-zinc diet (300 ppm) for 4 weeks and then treated daily with 160 ng prothymosin alpha, an increase occurred in resistance to infection with C. albicans, in the capacity to release MIF in vivo into the circulation and in the capacity of peritoneal macrophages to engulf (phagocytose) and kill cells of C. krusei. In addition, the number of spleen lymphocytes producing antibody to a T-dependent antigen was significantly increased in the mice fed a high-zinc diet and inoculated daily with prothymosin alpha.

Relationship of cytotoxic activity of natural killer cells to growth rates and serum zinc levels of female RIII mice fed zinc

This study examined a) the dietary zinc (Zn) requirement of RIII female weanling mice and b) the cytotoxicity of murine natural killer (NK) cells obtained from spleens of these mice fed varying levels of Zn. Zn was fed in a biotin-enriched egg albumen diet in amounts ranging from 0.9 to 40.4 micrograms/g diet. During a 28-day growth assay, maximum carcass growth was obtained with a diet containing 5.4 micrograms Zn/g diet. Maximal serum levels of Zn, however, were observed in mice fed diets containing 3.4 micrograms Zn/g diet. The cytotoxic activity of NK cells obtained from spleens of selected treatment groups was maximal at 40.4 micrograms Zn/g diet and was significantly higher (p less than or equal to 0.05) than that observed in spleens from mice fed diets that maximized carcass growth rates and serum Zn concentrations. It is concluded that female RIII mice have a dietary Zn requirement for growth similar to that observed for other murine strains but considerably lower than that reported for the rat. Our findings also suggest that RIII NK cells are particularly sensitive to dietary Zn intake: the optimal functional activity of these cells may result from intake of Zn higher than that necessary to maximize carcass growth and serum Zn concentrations.

Chronic zinc deficiency and listeriosis in rats: acquired cellular resistance and response to vaccination

The functional significance of zinc deficiency on primary and secondary host responses to infection with a facultative intracellular pathogen was studied in specific pathogen free rats. Groups of female rats fed either a low zinc or normal diet for 8 or 10 weeks were infected with Listeria monocytogenes five days prior to sacrifice. Zinc-deficient rats demonstrated thymic atrophy, reduced delayed hypersensitivity responses to listeria antigen, and impaired lymphocyte response of spleen cells to phytohemagglutinin, but not to Concanavalin A. Separate groups of zinc-deficient or control rats were vaccinated with viable L. monocytogenes 10 days prior to respiratory challenge. Vaccination resulted in successful control of bacteria in both dietary groups.

Serum and urine zinc response in head-injured patients

A prospective longitudinal evaluation of serum zinc concentrations was performed in 26 head-trauma patients, and 24-hour urine zinc excretion was determined in 15 of these subjects. Patients had markedly depressed admission serum zinc concentrations (mean +/- standard error of the mean: 40.2 +/- 3.2 micrograms/dl; normal values: 70 to 120 micrograms/dl), which gradually increased during the 16-day study period. All subjects demonstrated increased urinary zinc losses throughout the study period. Urinary zinc excretion was greater in patients with more severe head injuries. Indeed, patients with more severe head trauma had mean peak urinary zinc losses of greater than 7000 micrograms/day (normal less than 500 (micrograms/day). The implications of this altered zinc metabolism for protein metabolism, wound healing, and immune function, and the specific role of zinc in brain function and recovery from injury are discussed.

T-lymphocyte subsets and interleukin-2 production in zinc-deficient rats

1. It has been suggested that zinc-deficiency impairs cellular (T-lymphocyte-mediated) immune responses via a selective effect on helper T-lymphocytes. We have addressed this question in the rat by employing recently developed reagents in the form of monoclonal antibodies which specifically identify rat T-lymphocyte subsets (identifying total T-cells, helper T-cells and suppressor T-cells) and also by quantifying helper T-cell function by measurement of the helper T-cell-derived molecule interleukin-2 (IL-2). 2. Zn-deficiency induced T-cell atrophy (assessed morphologically and phenotypically with anti-rat T-cell monoclonal antibodies) in both peripheral blood and spleen. The use of these specific monoclonal antibodies failed to demonstrate a selective effect of Zn deficiency on the helper T-cell fraction of the total T-lymphocyte population. 3. In contrast, the results of functional assays of the T-lymphocyte response were dependent on the conditions of culture but suggested that the generation of IL-2 and its corresponding receptor were determined by the intracellular Zn status. Thus, in vivo, helper T-lymphocyte numbers are non-specifically reduced since other T-cell subsets are also reduced in response to appropriate stimulation. The functional consequences of this are dependent on the intracellular concentration of Zn but appear to influence both IL-2 production and its receptors on activated T-cells.

Subclinical trace element deficiency in children with undue susceptibility to infections

Serum concentrations of iron, copper, zinc and magnesium and also serum transferrin and ceruloplasmin were investigated in 28 children aged 10 months to 10 years with undue susceptibility to infections. None of the children had any classical immune defect. Seven of them had had frequent upper respiratory tract infections, 16 had suffered from frequent infections of the middle ear and five from mainly lower respiratory tract infections. Thirteen healthy children aged 9 to 18 years residing in the same area served as controls. The children with undue susceptibility to infections had significantly lower mean serum iron (p less than 0.05) and zinc (p less than 0.001) levels than the healthy controls. The mean serum concentrations of copper and magnesium and of transferrin and ceruloplasmin did not differ between the patients and controls. Children with frequent middle ear infections seemed to account for most of the differences in the serum levels of iron and zinc. An inverse correlation was observed between duration of breast feeding and serum concentration of zinc, and between weight as well as height and serum magnesium. The reasons for these changes and the possible role of trace element deficiency as a factor predisposing to or perpetuating undue susceptibility to infections in children are discussed.

Effects of dietary zinc on melanoma growth and experimental metastasis

These studies were designed to determine the effects of zinc on in vitro melanoma cell growth and in vivo metastasis. Cultured P51 mouse melanoma cells were larger, had longer doubling times and a decreased rate of tritiated-thymidine uptake when grown in zinc depleted compared to standard medium. Experimental metastasis was evaluated using intravenously injected, radiolabelled melanoma cells. Cell distribution and survival were determined 1, 3 and 21 days post-injection in C57BL/6 mice fed low zinc (0.5 and 4.0 mg Zn/kg) or stock diets. Altered organ distribution and survival of melanoma cells were observed in the zinc depleted dietary groups compared to the stock diet group. After 21 days of tumor growth, lungs of mice fed diets low in zinc contained up to 50% fewer labelled tumor cells than those of mice fed the stock diet. Livers of mice in the 0.5 mg Zn/kg group contained a greater percentage of tumor cells 21 days post-injection than those of mice fed the stock diet. Thus, dietary zinc can influence experimental tumor metastasis through modification in organ distribution of tumor cells and their subsequent survival.

Response to Mycobacterium bovis BCG vaccination in protein- and zinc-deficient guinea pigs

Groups of specific pathogen-free Hartley strain guinea pigs were vaccinated with viable Mycobacterium bovis BCG and maintained on isocaloric purified diets containing either 30 or 10% protein (ovalbumin) combined with either 50 ppm (microgram/g) or no added zinc. Seven weeks later the guinea pigs were skin tested with purified protein derivative and killed. Both protein and zinc deficiencies had a significant negative impact on growth of the guinea pigs. Both groups consuming the 10% protein diet also demonstrated significant reductions in hematocrit, total serum proteins, and serum albumin, as well as diminished spleen weight. Plasma zinc concentrations were reduced in both low-zinc groups to less than half the value observed in control guinea pigs. Protein deficiency, alone or combined with zinc deficiency, resulted in increased tissue levels of viable M. bovis BCG in the inguinal lymph nodes and subcutaneous vaccination nodule. These same groups exhibited significant impairment in the ability to mount a delayed hypersensitivity reaction. Phytohemagglutinin-driven polyclonal T cell blastogenesis in vitro was significantly diminished in the peripheral lymphocytes of both protein- and protein-zinc-deficient animals at low mitogen doses, but only in the protein-zinc-deficient guinea pigs as the dose of phytohemagglutinin was increased. These results suggest that dietary protein and zinc deficiencies, alone or combined, interfere with immunological responses of the host to vaccination with M. bovis BCG.

Effects of antigen stimulation and interleukin-1 on in vivo splenic zinc changes in the A/J mouse

The roles of zinc in immune responses continue to be defined and its impact on a broadening list of immune functions reported. Fundamental to the operation of zinc-dependent processes may be shifts in tissue zinc. Since the spleen is a site of activation, proliferation, and differentiation of lymphocytes, we examined changes in copper and zinc levels in spleens of antigen-stimulated A/J mice. Antigen stimulation with human immunoglobulin G and heat killed Staphylococcus aureus was compared with the actions of a nonantigenic inflammatory agent CaCl2. Between-group variations in copper and zinc with antigen treatment were compared in heart, liver, and spleen tissues. The zinc contents of spleens from antigen-treated mice were elevated, as were liver levels of the essential trace element. There were no significant increases in copper levels associated with antigen treatment. CaCl2-treated animal spleens demonstrated decreases in spleen copper and zinc content that were related to weight changes in the spleens, but not to specific treatment effects. Changes were suggestive of Interleukin-1 (IL-1) actions, which led to direct studies of IL-1 actions on splenic zinc. Partially purified IL-1 was injected into the tail vein and heart of A/J mice; liver and spleen zinc levels were determined 16 and 40 hours after injection. Significant increases in liver and splenic zinc concentrations were measured at both time intervals after IL-1 treatment. Antigen stimulation and, more directly IL-1, were related to stimulated increases in splenic zinc.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphocyte and granulocyte function in zinc-treated and zinc-deficient hemodialysis patients

Lymphocyte blast transformation and granulocyte motility were studied in 20 clinically stable hemodialysis patients, 10 of whom were receiving 50 mg of zinc (as zinc acetate) per day and 10 of whom were not. Plasma zinc concentration was significantly higher in zinc-treated than in untreated patients (108 +/- 5 vs. 82 +/- 2 micrograms/dl). Mononuclear cell subpopulation analysis showed equivalent proportions of T lymphocytes and monocytes in both groups, but B lymphocytes were reduced in untreated patients (10 +/- 0.7 vs 14 +/- 0.5%). Lymphocyte blast transformations in response to nonspecific mitogens, soluble antigen and mixed lymphocyte culture were not significantly different in the two groups, nor was lymphocyte zinc concentration. Zinc-treated patients showed significantly greater granulocyte responsiveness to zymosan-activated serum (21 +/- 1 vs. 14 +/- 2 mean), greater chemokinetic activity (50 +/- 4 vs. 27 +/- 3 mean) and higher granulocyte zinc concentration (114 +/- 6 vs. 47 +/- 2 micrograms/10(6) cells) than untreated patients. Granulocyte zinc correlated significantly with plasma zinc (r = 0.81, P less than 0.001) and with granulocyte motility (r = 0.63, P = 0.001). Moderate zinc deficiency in hemodialysis patients does not result in abnormal lymphocyte blast transformation in vitro, but it does result in granulocyte zinc depletion and impaired granulocyte motility.