Role of Zn2+ and other divalent metal ions in human lymphokine production in vitro

Parenteral zinc supplementation in adult humans during the acute phase response increases the febrile response

The acute phase response (APR) that follows injury or infection is characterized by a decrease in serum zinc concentrations, which we hypothesized benefits the host. Additionally, we proposed that preventing this decline by supplementing zinc would result in an exaggerated APR as indicated by elevated temperatures, increased serum cytokine concentrations, interleukin 6 and the acute phase protein (ceruloplasmin). A prospective, randomized, double-blinded, clinical trial was conducted. Patients on home parenteral nutrition with a diagnosis of catheter sepsis and patients with a diagnosis of pancreatitis, also on total parenteral nutrition (TPN), were recruited for the study. Following enrollment, block randomization was used to assign patients to receive 0 mg (n = 23) or 30 mg (n = 21) of zinc per day for the first 3 d of TPN. Blood samples for measurement of serum zinc, copper, ceruloplasmin and interleukin-6 were obtained upon enrollment and on d 1 through 3 of TPN. The highest temperatures reported on these days in the medical record were also recorded. Repeated measures ANOVA was used to determine differences in the primary outcome variables over time. No significant differences between groups were observed in serum interleukin-6 or ceruloplasmin concentrations. A significantly higher (P = 0.035) temperature was observed in the zinc-supplemented group compared with the control group on d 3 of parenteral nutrition. We conclude that parenteral zinc supplementation in patients experiencing a mild APR resulted in an exaggerated APR as evidenced by a significantly higher febrile response.

Serum trace element levels in HIV-infected subjects

The absolute number of T4 cells and the serum concentrations of Ca, Cu, Fe, K, Mg, P, Se, and Zn were determined in 59 Walter-Reed staged, HIV-infected men, compared to healthy controls, serum levels of Ca, Cu, and Fe were significantly higher, those of P and Se significantly lower in the HIV-infected subjects. In the HIV-infected cases, but not in the controls, the concentrations of Se and Zn, of Ca with Cu and Fe, and of Fe with P, were directly correlated. In the controls, the correlation between the levels of K and Mg was direct, and inverse between those of Zn and P. Trace element levels did not significantly correlate with WR-stage. However, the absolute number of T4 cells was directly correlated with the serum Mg concentration.

Differential effects of copper and zinc on human peripheral blood monocyte cytokine secretion

The addition of copper and zinc salts to human peripheral blood leukocytes cultured in complete medium containing endotoxin and fetal calf serum stimulated tumor necrosis factor (TNF) secretion in a concentration-dependent manner. The secretion of interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) was inhibited by copper under the same culture conditions, while zinc stimulated IL-1 beta secretion in a concentration-dependent manner and had no effect on leukocyte IL-6 release. Both copper and zinc induced increases in TNF mRNA (54 and 14%, respectively) when compared to cells cultured in complete medium alone. In serum-free, low endotoxin medium (less than 6 pg/ml), both copper and zinc failed to stimulate either TNF or IL-1 beta secretion. Under the same conditions the addition of lipopolysaccharide (LPS), at concentrations above 0.01 micrograms/ml, induced a concentration-dependent release of both cytokines. When either copper or zinc were combined with 0.01 micrograms/ml LPS, a synergistic stimulation of TNF secretion resulted. IL-1 beta secretion, unlike TNF, was not synergistically stimulated by combining metals and LPS in serum-free medium. Combining copper and zinc with inhibitors of TNF secretion, transforming growth factor beta, prostaglandin E2, and plasma alpha-globulins, resulted in a reduction of the suppressive effects of each of these agents. This study suggests that the trace metals copper and zinc may play important and possibly distinct roles in regulating leukocyte secretion of TNF, IL-1 beta, and IL-6.

Extracellular metallothionein effects on lymphocyte activities

Metal cation influences on the immune response have been reported in a wide variety of experimental systems. These influences can either result in the augmentation or suppression of immunological activities. In order to investigate possible mechanisms of these influences, we examined the role that a metal cation-induced protein, metallothionein (MT), might play. Our findings suggest that thioneins, either as apoproteins or when complexed as Cd,Zn-MT, Zn-MT, or Cd-MT, are capable of inducing lymphocyte proliferation. This level of induction is substantially reduced when Zn,Cd-MT is added to lymphocyte cultures in the presence of 50 microM 2-mercaptoethanol. Apoprotein, Zn,Cd-MT, Zn-MT and Cd-MT also augment LPS-induced proliferation of splenic lymphocytes. Only the Zn,Cd-MT preparation significantly augmented ConA-induced proliferation. Hg-MT and Cu-MT were inhibitory as additions in either LPS or ConA mitogen proliferation assays, and did not stimulate proliferation when added alone to lymphocyte cultures. The capacity to induce proliferation correlates with the measurable thiol level of the particular thionein. Interestingly, Zn,Cd-MT and apothionein had an equivalent number of accessible thiols. Although Zn, Pb, Hg and Cu lowered the number of these sites, the immunoreactivity of these MTs was not altered substantially except by Pb. These results suggest that some metal influences on lymphocytes might be through a thionein intermediary. Our results also demonstrate that thioneins complexed with certain metal cations are detrimental to the normal cellular activities of lymphocytes. At least in these circumstances, MT does not play a role as a protective agent.

Activation of thymocyte responses to interleukin-1 by zinc

In vitro proliferative responses of murine thymocytes to interleukin-1 are enhanced by supplementing the cultures with the trace nutrient zinc. Zine not only enhances the responses of cells suboptimally activated by PHA but can also prime the cells to respond to IL-1 in the absence of activation by PHA. Zinc affects the early stages of the proliferative response. The data suggest that zinc may enhance the cellular uptake of IL-1 or may facilitate enzymatic steps subsequent to IL-1 binding.

Induction of interferon-gamma in human leukocyte cultures stimulated by Zn2+

Our studies have confirmed previous reports that Zn2+ has a mitogenic effect on human lymphocytes. Furthermore, we have tested the ability of Zn2+ to induce interferon production in human leukocyte cultures. Peripheral blood mononuclear cells were stimulated with ZnCl2 at different concentrations. Interferon was detected in the supernatants of cultures stimulated with concentrations ranging from 5 X 10(-4) to 5 X 10(-5) M. Interferon was produced only in the presence of accessory cells. The type of interferon induced by Zn2+ was interferon-gamma, as proven by the use of specific antisera.

Supplemental zinc (Zn2+) restores antibody formation in cultures of aged spleen cells. II. Effects on mediator production

In vitro antibody production to T-dependent erythrocyte antigens is depressed as a function of age. Supplementation of antibody-forming cultures with the essential trace element zinc restores the capacity of cells from immunodepressed, aged mice to generate an antibody response. Zn2+ produces maximal enhancement of immune function when it is added to the cultures within the first 24 h. Supernatants obtained from cultures supplemented with zinc from 0-24 h contain soluble, nondialyzable factors which support enhanced antibody production in fresh cultures of cells from aged mice. Interleukin 2 levels in the supernatants from Zn2+-supplemented cultures were not increased. However, the levels of interleukin 1 were increased approximately 300% over nonsupplemented controls and these increases corresponded with the ability of the supernatants to support antibody formation. Further studies showed that, in addition to enhancing the production of interleukin 1, Zn2+ enhanced the ability of concanavalin A-activated T cells from aged mice to produce B cell stimulatory factor-1.

Stimulation of murine lymphocyte responses by cations

The capacity of the heavy cations Pb, Ni, and Zn to modulate murine in vitro lymphocyte responses was examined. Pb and Ni (100 microM) were shown to enhance the in vitro plaque-forming cell (PFC) response to sheep red blood cells while 100 microM Zn had inhibitory effects. Each metal was able to stimulate the proliferation of murine splenocytes as determined by [3H]thymidine incorporation and autoradiography. The enhancing effect of the metals on the PFC response was observed whether the results were expressed on a per culture or a per cell basis, indicating an actual increase in B-cell differentiation. Both the PFC response and the proliferative response were shown to be sensitive to the type of medium employed (M-199 gave optimum results) and to the presence or absence of 2-mercaptoethanol. As in autologous mixed-lymphocyte responses peak proliferation occurred after Day 5 in culture, was cell density dependent, and required the presence of both T cells and Ia+ cells. Treatment of splenocytes with anti-Thy-1.2, anti-Lyt-1, or anti-L3T4 plus complement completely abrogated the proliferative response, indicating that a Lyt-1+, Lyt-2-, L3T4+ T-cell was required for the induction of proliferation. The data are consistent with the hypothesis that the metals are capable of modifying the immune response directed at self either by directly altering self constituents (class II) or by modulating the autologous T-cell response.

In vitro modulation of murine natural killer cytotoxicity by zinc

The in vitro effects of zinc on natural killer (NK) activity of murine spleen cells were studied. The pretreatment of splenocytes with non-toxic concentrations of ZnSO4 induced a decrease of lytic activity against YAC-1 and RDM4 targets. The lytic function of non-activated and poly(I) X poly(C)-activated NK cells was similarly inhibited. When the interaction of effector cells with zinc was studied for 5 min, a significant inhibition of NK lysis was noted, which was maximal after 30 min. Zinc was undoubtedly responsible for the observed effects, since the concurrent addition of both zinc and suitable concentrations of o-phenanthroline, a Zn++ chelating agent, made it possible to maintain a normal level of lysis. Moreover, the pretreatment of spleen cells with increased concentrations of o-phenanthroline also inhibited NK lysis, suggesting that a physiological intracellular zinc content is required to maintain an optimal lytic function of NK cells. Although the lysis was completely suppressed after the addition of 10(-4) M ZnSO4, the frequency of target-binding cells (TBC), which was assumed to represent the first stage of NK-mediated cytolysis, was only partly inhibited. The results are discussed in view of a possible action of zinc on cell membrane functions, enzyme systems, and release of lymphokines.

Role of monocytes/macrophages and interleukin 1 in antigen-induced human lymphokine production

The monocyte/macrophage (M phi)-dependency for antigen-induced production of the lymphokine, leukocyte migration inhibitory factor (LIF), was investigated using a M phi pulse-exposure technique. M phi-depleted, purified T lymphocytes did not elaborate LIF in response to the recall antigen, tuberculin (PPD). Addition of M phi's pulsed with PPD rectified the response. Exposure of the M phi's down to 3 min, even at 0 degree C, was efficacious. PPD-exposed M phi's, either killed or rendered incapable of protein synthesis, failed to activate the T cells. However, PPD-exposed, killed M phi's triggered LIF production if exogenous interleukin 1 (IL-1) was provided. We suggest that M phi "presentation" of antigen in this test system is a passive albeit necessary, process; the requirement for M phi metabolism being confined to the elaboration of IL-1. Judged by the results of kinetic experiments, the latter stimulus appears to be mediated most effectively from 2 to 4 hr after antigenic challenge.

Immunosuppressive actions of gold salts

In rheumatoid arthritis both lymphocyte-mediated and antibody-mediated immune reactions are important for the inflammatory lesions. In vivo activated B lymphocytes/plasma cells, T lymphocytes and monocytes/macrophages (Mo) are intimately involved in the disease process. Several clinical observations suggest an immunosuppressive action of gold salts. In humans, gold salts interfere with a number of Mo functions in vitro, including cellular interactions between Mo and T lymphocytes. Some workers have shown that the activation of human T lymphocytes is inhibited by gold salts, most probably secondary to an inhibition of Mo-T cell cooperation. Recent experiments indicate that gold salts also affect the in vitro differentiation of human B lymphocytes in response to polyclonal activators. Both the gold atom and the SH group seem to be important for the immunosuppressive actions of gold salts.

Effects of cyclosporin A (CyA) and methylprednisolone (MP) on the immune response. I. T-cell-activating factor abrogates CyA- but not MP-induced suppression of antigen-induced lymphokine production

The influence of cyclosporin A (CyA) and methylprednisolone (MP) on the elaboration of the human lymphokine, leukocyte migration inhibitory factor (LIF) was investigated. Both CyA and MP at pharmacological concentrations inhibited the release of LIF from immune lymphocytes challenged by recall antigen. By contrast, the release of LIF in response to polyclonal activation by phytohaemagglutinin A was not affected by CyA or by MP. CyA and MP had no effect on the production of the monokine, T-lymphocyte-activating factor (TAF) by stimulated blood monocytes. However, addition of partially purified TAF to antigen-stimulated lymphocytes completely abrogated the inhibitory effect of CyA, but not that of MP. Thus, CyA and MP affect antigen-induced production of LIF by immune lymphocytes by different mechanisms.

Involvement of monokines in antigen- and lectin-induced human lymphokine production

To analyze the role of monocytes/macrophages (Mø's) in the activation of human lymphocytes, suspensions enriched in T cells and markedly depleted of Mø's were prepared. The Mø-depleted cells challenged by tuberculin did not elaborate the lymphokine, leukocyte migration inhibitory factor (LIF). This reduction in LIF production was negatively correlated to the proportion of residual Mø's being complete in the presence of less than 2% Mø's. In contrast, the LIF response to the polyclonal activator, phytohemagglutinin A, was unimpaired by Mø depletion. LIF production of the Mø-depleted cells could be fully reconstituted by addition of conditioned media obtained from Mø cultures, especially if stimulated by the Mø-activating agent, phorbol myristate acetate. This effect was dose-dependent and could be ascribed to molecules of molecular weights 80K and 12K, respectively.