Antibody suppression by cadmium

Toxic elements and associations with hematology, plasma biochemistry, and protein electrophoresis in nesting loggerhead sea turtles (Caretta caretta) from Casey Key, Florida

Toxic elements (arsenic, cadmium, lead, mercury, selenium, thallium) are a group of contaminants that are known to elicit developmental, reproductive, general health, and immune system effects in reptiles, even at low concentrations. Reptiles, including marine turtles, are susceptible to accumulation of toxic elements due to their long life span, low metabolic rate, and highly efficient conversion of prey into biomass. The objectives of this study were to (1) document concentrations of arsenic, cadmium, lead, mercury, selenium, and thallium in whole blood and keratin from nesting loggerhead sea turtles (Caretta caretta) from Casey Key, Florida and document correlations thereof and (2) correlate whole blood toxic element concentrations to various hematological and plasma biochemistry analytes. Baselines for various hematological and plasma analytes and toxic elements in whole blood and keratin (i.e., scute) in nesting loggerheads are documented. Various correlations between the toxic elements and hematological and plasma biochemistry analytes were identified; however, the most intriguing were negative correlations between arsenic, cadmium, lead, and selenium with and α- and γ-globulins. Although various extrinsic and intrinsic variables such as dietary and feeding changes in nesting loggerheads need to be considered, this finding may suggest a link to altered humoral immunity. This study documents a suite of health variables of nesting loggerheads in correlation to contaminants and identifies the potential of toxic elements to impact the overall health of nesting turtles, thus presenting important implications for the conservation and management of this species.

Mechanism of cadmium induced apoptosis in human peripheral blood lymphocytes: the role of p53, Fas and Caspase-3

Cadmium (Cd) is a major pollutant of environment. It can be fatal to human. In spite of bulk of research and literatures, the mechanism of a fatality against human is still not understood completely. Toxic and carcinogenic effects of Cd in rodents and humans are well known. However, effects of Cd on induction of apoptosis are still elusive. This study indicates immunosuppression and immunotoxicity due to Cd exposure. Present study was undertaken to determine the mechanism of cell death in vitro in human peripheral blood lymphocytes induced by Cd. Our findings suggest the toxicity due to Cd is attributed to programmed cell death-apoptosis. IC₅₀ was calculated at 21.74 μM. A significant increase of expression of the pro-apoptotic genep53, Fas and Caspase-3 in human lymphocytes was found. Cd induced p53-dependent apoptosis through cooperation between Bak upregulation without changing the Bcl-2 and Bax expression. Data of this study compel to speculate that apoptosis may also be attributed to CD95/Fas complex formation, and p53 direct apoptogenic potential at mitochondria. It was confirmed by the increased expression of Caspase-3. Although, this work does not address all the questions regarding the mechanism of Cd induced apoptosis, but these findings establish an important role of p53 and mitochondrial function during apoptosis in human lymphocyte. Moreover, based upon our findings, the role of Fas in Cd induced apoptosis is also undeniable. Hence further investigations are required to understand the different mechanism involved into apoptosis of lymphocytes due to Cd exposure.

Heavy metal exposure, reproductive activity, and demographic patterns in white-footed mice (Peromyscus leucopus) inhabiting a contaminated floodplain wetland

We examined the concentrations of selected metals and selenium (Se) in the tissues of white-footed mice (Peromyscus leucopus) collected at a constructed wetland originally created as a retention basin for sediments dredged from Lake DePue, Illinois. These sediments were contaminated with high concentrations of cadmium (Cd), zinc (Zn), and other elements as a result of nearby smelting operations. White-footed mice inhabiting the former retention basin experienced greater exposure to Cd, Pb, and Se than those from nearby reference sites. Concentrations of Cu and Zn in livers of mice from the contaminated wetland and adjacent floodplain reference site were greater than in mice from the more-distant reference sites. Judging by concentrations in their kidneys, white-footed mice inhabiting the floodplain adjacent to the contaminated wetland had greater exposure to Cd than those from the two more-distant reference sites. Concentrations of Hg in tissues of mice did not vary appreciably among sites. Concentrations of Cd and Se in the tissues of some white-footed mice from the contaminated wetland exceeded critical concentrations observed in experimental studies of laboratory mice and rats; with few exceptions tissue Pb concentrations were below published effects levels. However, we did not detect changes in abundance, demographics, or reproductive activity that might suggest population-level effects of contaminant exposure. Mean weight of embryos expressed as a function of crown-rump length did not differ among locations sampled, and no gross lesions indicative of exposure to heavy metals were observed. Kidney and liver weight, corrected for body weight, were nominally, though not significantly, lowest in both male and female mice from areas of increased Cd and Pb exposure. Metals dredged from Lake DePue were still bioavailable 25 years after deposition. However, small mammal populations are resilient to environmental stressors and we did not detect differences in population parameters suggesting that the population of white-footed mice inhabiting the contaminated wetland was at risk from increased exposure to these contaminants.

Humoral and cell mediated immune response to cadmium in mice

The effect of 30, 100 and 300 ppm of cadmium chloride (CdCl2) exposure for 35 days on humoral and cell mediated immune response was examined in Swiss Albino mice. Body burden of cadmium in kidney, spleen and liver was determined and histopathology of these organs was also done. Cadmium chloride in doses of 100 and 300 ppm when fed in drinking water caused significant decrease in IgM and IgG titre against sheep red blood cells (SRBC) and a significant decrease in IgG titre against bovine serum albumin (BSA). The delayed type hypersensitivity response to SRBC and splenic T cell proliferation to BSA was also significantly decreased following 100 amd 300 ppm cadmium exposure. Cadmium accumulation in the spleen, liver and kidney was associated with degeneration and inflammatory changes. It is concluded that cadmium causes significant suppression of humoral and cell mediated immune response in mice which could be due to its cytotoxic action on liver, kidney and immune cells.

Effects of chromium on humoral and cell-mediated immune responses and host resistance to disease in a freshwater catfish, Saccobranchus fossilis (Bloch)

The effects of subtoxic levels of Cr on humoral and cell-mediated immune responses, blood parameters, susceptibility to bacterial (Aeromonas hydrophila) infection, and macrophage activity in the freshwater air-breathing Asian catfish, Saccobranchus fossilis, during a 28-day exposure were examined by a static bioassay test procedure. At 0.1, 1.0, and 3.2 mg / liter Cr, dose-dependent Cr accumulation in kidney, liver, and spleen was observed at the end of the experiment. Chromium exposure caused a significant change in spleen to body weight ratio. Fish exposed to Cr concentrations had lower antibody titer values, reduced numbers of splenic and kidney plaque-forming cells, and higher counts of splenic lymphocytes but reduced counts of kidney cells when compared with the control group. At 0.1, 1.0, and 3.2 mg /liter Cr, dose-dependent decreases in red blood cell counts, hemoglobin content, and packed cell volume were observed. Differential leukocyte counts revealed that Cr exposure caused a significant decrease in large and small lymphocytes, whereas neutrophils and thrombocytes increased. Effects of Cr exposure to mitogen (Con A) on proliferation of splenic and pronephric lymphocytes suggests a decrease in mitogenic response. The eye-allograft rejection time, as a parameter of cell-mediated immunity, was statistically increased at 1.0 and 3.2 mg/liter Cr. Fish exposed to Cr for 28 days exhibited higher susceptibility to A. hydrophila infection than control fish. The results suggest that Cr exposure reduced the resistance of catfish to bacterial infections. The phagocytic activity of splenic and pronephros macrophages was examined in vitro and found to be significantly decreased.

Effect of cadmium body burden on immune response of school children

The effects of cadmium on measures of immune-system function were determined from a health survey of school children in heavily polluted regions of eastern Germany. A representative sample of 842 students, aged 5-14 y, was included in logistic regression analyses in which the relationship between urinary cadmium content and blood immunoglobulin levels was examined. Investigators further evaluated a subsample of 807 students to determine cadmium's effect on the immediate hypersensitivity reactions elicited by skin-prick challenges with 12 common aeroallergens. Several potentially confounding factors were controlled for, after which investigators found that increasing body burdens of cadmium were associated consistently with dose-dependent suppression of immediate hypersensitivity and of immunoglobin G, but not immunoglobulins M, A, or E levels. The immunoglobulin pattern observed in exposed children led investigators to suggest that secondary humoral responses were impaired by cadmium.

Influence of inhaled cadmium on the immune response to influenza virus

Cadmium may exacerbate pulmonary infections. In a previous study, however, cadmium appeared to enhance mouse resistance to influenza pneumonia. We report herein on the influence of cadmium intoxication in mice on different factors of anti-influenza immunity, e.g., antibody response, local production of interferon, pulmonary cellular response, and the interaction between pulmonary alveolar macrophages and the influenza virus. Cadmium inhalation did not affect production of antibodies or interferon. The protective effect appeared to be related to an enhanced supply to phagocytic cells into the lung.

Effects of mainstream and environmental tobacco smoke on the immune system in animals and humans: a review

This review evaluates the available information on the effects of mainstream and environmental tobacco smoke on the immune system in animals and humans. The primary emphasis is on mainstream smoke since little information is available on the effects of environmental smoke. The effects of mainstream tobacco smoke on the immune system in humans and animals are similar. Animals exposed to mainstream tobacco smoke for periods of a few weeks generally exhibit a slight immunostimulation. However, subchronic and chronic exposure studies indicate that immunosuppressive changes develop. Lymphocyte proliferation in response to the mitogens PHA and LPS is decreased, suggesting compromise of cell function. Antibody production can be suppressed. Smoke-exposed animals that are challenged with metastasizing tumors or viruses have been shown to exhibit a higher incidence of tumorigenic and infectious diseases, respectively. Localized immunological changes in the lung can include reduction of bronchus-associated lymphoid tissue and immunoglobulin levels. Smoking-related changes in the peripheral immune system of humans have included elevated WBC counts, increased cytotoxic/suppressor and decreased inducer/helper T-cell numbers, slightly suppressed T-lymphocyte activity, significantly decreased natural killer cell activity, lowered circulating immunoglobin titers, except for IgE which is elevated, and increased susceptibility to infection. The effects of environmental tobacco smoke on the immune system, in contrast to mainstream tobacco smoke, have just begun to be investigated and information available in the literature, to date, is limited. Immunoreactive substances are known to be present in environmental tobacco smoke, but to date, environmental tobacco smoke has been more closely associated with irritation than sensitization. A few studies have indicated a potential for environmental smoke-induced hypersensitivity and suppression of immunoregulatory substances. In contrast, other investigators have failed to detect immunological or other biological changes associated with environmental smoke. Clearly, more research is needed to resolve these differences.

Effects of cadmium on lymphocyte activation

The effects of cadmium (Cd) on phytohemoagglutinin or phorbol myristate acetate-induced lymphocyte activation were investigated and a dose-dependent inhibition of cell proliferation was found. Kinetic studies revealed that the Cd-sensitive step is an early event of T cell stimulation. Failure of IL2 secretion and reduction of IL2 receptor expression in the Cd-treated cells are also reported. Regardless of which mechanism is responsible for Cd effects, our studies show that the inhibition of lymphocyte activation is associated with reduced [3H]phorbol dibutyrate binding to Ca2+-phospholipid-dependent protein kinase and altered breakdown of phosphatidylinositols. Thus, Cd interferes with two biochemical events which play a critical role in lymphocyte signal transduction and activation.

Immunological alterations and chemical exposure

The complex nature of the immune system with its multiple humoral and cellular components makes it an easy target for many drugs and chemicals. Immunotoxicology is defined as an adverse response of the immune system to a chemical or drug which may result in disease such as autoimmunity, immune suppression, allergy or other hypersensitivity states. Occasionally, immune enhancement is the end result. Because many of the immune system's cellular and humoral components can be isolated and studied in vitro, assays have been developed to study the immunotoxic effects of chemicals. Further refinement of these in vitro studies is required along with clinical investigations into the effects of chemicals on the immune system of humans. Extrapolating from the animal data to human effects has proven to be unsuccessful in many circumstances. Further definition and study of immunotoxic responses as contrasted with normal immune responses to neo-antigens are required to investigate actual disease causation.

Modulation of murine T and B cell reactivity after short-term cadmium exposure in vivo

This study assessed early effects of short-term Cd exposure on T and B cell responsiveness. Spleen cells from mice injected s.c. with a daily dosage of 1 mg, 0.33 mg, or 0.11 mg Cd (as CdCl2) per kg body weight for 5 days were examined for their potential to generate alloreactive T cells in a mixed lymphocyte reaction (MLR) and for mitogen reactivity to concanavalin A (Con A) in vitro. Spleen cells from the same mice were also assayed for the total number of IgM- and IgG-secreting B cells. Whereas alloreactivity was reduced, mitogen response to Con A was not different from controls or was even enhanced. The decrease in allogeneic MLR was dependent on the injected Cd dosage. No difference in susceptibility to Cd-induced effects was observed among the mouse strains tested, i.e. BALB/c, DBA/2, C57BL/6, and C3H/He. Co-cultivation of spleen cells, obtained from Cd-treated mice that exhibited deficient T cell reactivity, with splenic responder cells from untreated mice resulted in dose-dependent suppression of the normal MLR. These results indicate that the harmful effects of Cd on the immune system include the inhibition of antigen-specific T cell responses by the activation of an antigen non-specific suppressor system. In contrast to the suppressed allogeneic MLR, the same spleen cell populations showed augmented numbers of IgM- and IgG-antibody producing cells.

Immunosuppression in mice after inhalation of cadmium aerosol

Aerosol cadmium (CdCl2) exposure of female C57Bl/6 mice was performed to assess the in vivo effects of cadmium on the cellular and humoral immune responses of splenic lymphocytes. Primary cellular and humoral responses of lymphocytes were examined at 5-18 days after a single, 60 min exposure to 0.88 mg Cd/m3 (MMAD = 0.7 +/- 0.3 micron, sigma g = 3.43). Significant decrease of in vitro lymphoproliferative response to allogeneic antigens, LPS and PHA antigens, and inhibition of the primary IgM response to sheep erythrocytes were correlated with a marked decrease in spleen cell viability at 5-8 days after aerosol cadmium exposure. This type of cadmium-induced immunosuppression, which correlated with the direct cytotoxicity of effector cells, appeared to be different from the chronic, oral cadmium-induced suppression of the primary IgM response, in which acute cytotoxicity of the spleen cell population was not observed.

The effect of cadmium on chemical- and viral-induced tumor production in mice

Female Swiss mice were exposed to cadmium in the drinking water at concentrations ranging from 0 to 50 ppm for 105 or 280 day time periods. In the 105 day study, the effect of cadmium on urethan-induced pulmonary adenoma formation was evaluated. Urethan-induced sleeping times observed following i.p. injection of urethan after 3 weeks of cadmium exposure were not affected by cadmium indicating that chronic cadmium exposure did not alter the elimination of urethan. Pulmonary adenoma formation which was evaluated 84 days later was not affected by cadmium. The size and number of tumors remained unchanged. This suggests that the immunosuppressive actions of cadmium do not influence urethan-induced adenoma formation. In the 280-day study, the effects of cadmium on the incidence of spontaneous murine lymphocytic leukemia was evaluated. Mortality from the leukemia virus was greater in the cadmium-exposed mice. Mice exposed to 10 or 50 ppm cadmium experienced 33% more deaths from the virus. The average time till death was unaffected. It appears that the immunosuppressive effects of cadmium impair immunosurveillance mechanisms that control expression of the murine lymphocytic leukemia virus.

Strain differences in cadmium-mediated suppression of lymphocyte proliferation in mice

Strain differences were investigated on the proliferative responses of splenic lymphocytes obtained from C3H/He, BALB/c, and DBA/2 mice that were treated with cadmium (Cd) for 5 days (0.5 or 1.0 mg Cd/kg/day, sc), and the results were compared with those of in vitro treatment of spleen cells with Cd. Following in vivo treatment, splenocytes from the C3H strain were significantly more susceptible to suppressive effects of Cd exposure on all indices for proliferative responses to mitogens (concanavalin A, phytohemagglutinin, and lipopolysaccharide) and allogeneic lymphocytes, while those from DBA and BALB strains were fairly resistant. Among the three strains, the highest Cd concentrations in plasma and spleen were obtained in the C3H strain with the lowest hepatic concentration of Cd. On the other hand, the Cd exposure hardly affected the splenic concentration of zinc in the C3H strain in contrast to its decrease in the others. When spleen cells obtained from normal mice were treated in vitro with Cd, the C3H strain was more resistant to the suppressive effect of Cd than the other strains. These results indicate that the mouse strain variations in Cd-mediated suppression of lymphocyte proliferation are not based on intrinsic lymphocyte sensitivities, but likely are due to differences in the metabolism of Cd, which is under genetic control.

Paradoxical effects of cadmium exposure on antibacterial antibody responses in two fish species: inhibition in cunners (Tautogolabrus adspersus) and enhancement in striped bass (Morone saxatilis)

Previous work in a marine fish, the cunner (Tautogolabrus adspersus), showed that endocytosis of bacteria by cells in the liver and spleen was affected by 96-h exposure of the fish to cadmium at a concentration of 12 micrograms/ml; however, antibody response to sheep erythrocytes was not affected. Since the latter finding was questionable because of short immunization times, and data from more than a single fish species were desirable, both the cunner and an anadromous fish, the striped bass (Morone saxatilis), were examined for antibody responses against the bacterium Bacillus cereus in Freund's complete adjuvant during a 6- to 8-wk time period. Exposure to 12 micrograms/ml cadmium caused significant inhibition of serum antibody titers (P less than 0.007) in cunners. Paradoxically, antibody response in striped bass exposed to 10 micrograms/ml cadmium was enhanced sixfold. This enhancement was weaker but still evident when the antigen was injected 48 d after cadmium exposure. Peritoneal exudate cells from cadmium-exposed striped bass also showed more active migration through microporous filters than cells from non-exposed fish. Since the 96-h cadmium LC50 was 26 micrograms/ml for cunners and 20 micrograms/ml for striped bass, the differences in antibody response could not be explained on the basis of differences in cadmium toxicity. Although geometric mean liver cadmium levels after exposure at 15 degrees C were higher in cunners (163.8 +/- 1.2 micrograms/gm) than in striped bass (64.4 +/- 1.2 micrograms/g), cunners exposed to cadmium at 2 degrees C had lower cadmium levels (46.4 +/- 1.2 micrograms/g) which were still effective in inhibiting antibody production at 8 degrees C. On the other hand, striped bass not exposed to cadmium showed a strong, exponential rise in serum antibody when the temperature at immunization, 14 degrees C, was reduced to 9 degrees C; whereas cunners held in the same tanks exhibited a weaker, biphasic serum antibody response. Regardless of the cause (innate differences in cellular response, or better stress adaptability in an anadromous fish), the data show that chemical-stress effects on the immune system of one fish species cannot be extrapolated to another species.

Effects of cadmium and lead on oxidative metabolism and phagocytosis by mouse peritoneal macrophages

We investigated the effects of cadmium and lead on the oxidative metabolism of mouse peritoneal macrophages induced either by phagocytosis of zymosan particles or by membrane perturbation with phorbol myristate acetate (PMA) without phagocytosis. Oxidative metabolism activity was measured by chemiluminescence in the presence of lucigenin. Furthermore, cell viability was tested by dye exclusion test and phagocytic activity was measured by ingestion of latex particles. Within the first hour of exposure to the metals the effects of cadmium and lead in peritoneal macrophages were the same. The oxidative metabolism induced by PMA was enhanced by both metals, the zymosan-induced oxidative metabolism was reduced, markedly by cadmium and weakly by lead. Cell viability was not affected. After 20 h of exposure the effects of cadmium and lead were different. Cadmium did not alter either the oxidative metabolism induced by zymosan and PMA or phagocytosis of latex-particles. Lead concentration-dependently suppressed the oxidative metabolism induced by zymosan and PMA as well as phagocytosis of latex-particles. However, cadmium reduced cell viability concentration-dependently in contrast to lead that reduced cell viability only slightly.

The effect of cadmium on antibody responses to antigens with different cellular requirements

Six week old BDF1 or CD-1 female mice were exposed to cadmium chloride in the drinking water at concentrations ranging from 0 to 50 ppm cadmium for 3 weeks. The in vivo antibody response against dinitrophenyl-aminoethylcarbamylmethyl-Ficoll (DNP-Ficoll), a T-lymphocyte independent, macrophage dependent response, was enhanced by cadmium. Similarly, the in vivo antibody response against Escherichia coli 0127 (LPS), a T-lymphocyte and macrophage independent response, was also enhanced by cadmium. In contrast, the in vitro antibody response against sheep red blood cells (SRBC), a T-lymphocyte and macrophage dependent response, was suppressed in spleen cell cultures that contained cadmium-exposed non-adherent cells (lymphocytes). Cultures containing cadmium-exposed adherent cells (macrophages) were not suppressed by cadmium. These results suggest that the immunosuppressive effects of cadmium as it relates to humoral immunity involve T-lymphocyte function rather than macrophage or B-lymphocyte activity. The enhanced T-lymphocyte independent antibody responses which accompany suppressed T-lymphocyte-dependent responses following cadmium exposure are an indication of compensatory mechanisms that are associated with the immune system.

Toxicity of cadmium chloride in vitro: indices of cytotoxicity with the pulmonary alveolar macrophage

Pulmonary alveolar macrophages were isolated from adult, male New Zealand white rabbits by bronchial lavage and exposed to cadmium chloride in vitro. The observed cell sensitivity to this metal was highly dependent upon the incubation conditions used as well as the cytotoxic index selected. An LC50 value, as measured by dye exclusion (erythrosin B), was determined to be 390 microM when these cells were exposed to cadmium in Ham's F12 culture medium for 8 hr at 35 degrees C. The presence of fetal calf serum in the medium (10%; v/v) enhanced this toxicity slightly, LC50 = 235 microM, as did raising the incubation temperature to 37 degrees C, LC50 = 201 microM. No effect on cadmium toxicity was observed when the culture medium was made deficient in Cu, Zn, and Fe, nor was there any effect observed when Hepes buffer was substituted for the bicarbonate/carbon dioxide buffering system. Measurements of cadmium-109 uptake by pulmonary alveolar macrophages were consistent with and could explain, at least in part, the above observations of cytotoxicity. In the standard culture system (an 8-hr exposure period at 35 degrees C in Ham's F12 culture medium plus serum), the appearance in the culture medium of two lysosomal enzyme activities, acid phosphatase and cathepsin D, paralleled cell death. In addition, an EC50 value of 102 microM was found for cadmium when cell respiration (O2 uptake) was measured; an EC50 value of 31 microM was found for cadmium when cell function (engulfment of killed yeast particles) was followed; and scanning electron microscopic studies showed cell membrane changes (loss of fine structure and blebbing) at cadmium concentrations as low as 30 microM. These findings suggest that loss of cell function and/or changes in cell morphology are more sensitive measurements of macrophage exposure to cadmium than is either cell death, lysosomal enzyme release, or cell respiration.

Immunopathology of chronic cadmium administration in mice

Young male mice were given drinking water containing 50 ppm cadmium (Cd) for 3 weeks, and were killed 0, 3 and 6 weeks after the cessation of treatment. At 0 weeks, suppression in the number of splenic plaque-forming cells in response to sheep red blood cell immunization was noted 5 days after antigen injection, but not 7 days after injection. Plasma IgG concentration and thymic factor activity were unaffected at 0 weeks. The number of circulating lymphocytes tended to be less in the Cd-treated mice at all times. Cd treatment had no effect upon liver and kidney weights, and upon the weights and the lymphocyte contents of the thymus and spleen at any of the observation times. Employing immunofluorescence with anti-mouse IgG and C3, no evidence of an autoimmune response was found in the kidney of the treated mice at 0 and 3 weeks. Mitochondrial abnormalities in the renal proximal tubule cells were noted at 0 weeks in the Cd-treated mice. The Cd concentrations of the liver and kidneys remained high at all observation times. The results suggest that a modest dose of Cd produces some depression of the immune system, and the biological half-life of Cd is long.

Evaluation of host resistance and immune function in cadmium-exposed mice

Adult female B6C3F1 mice received distilled water only or water containing 10, 50, or 250 ppm of cadmium chloride (CdCl2) for 90 days. Body weights were measured weekly. On selected days during exposure and on Day 91, Cd tissue concentrations were measured along with changes in primary antibody responses. On Day 91 mice also received a primary challenge with various infectious agents. T- and B-cell mitogenesis, natural killer (NK) cell function, delayed type hypersensitivity (DTH) as well as macrophage bactericidal activity, and phagocytosis were measured. There was no change in body weight gain, organ weights, or in humoral immunity during treatment even though cadmium had accumulated in significant quantities in the tissues. Compared with controls, exposure to cadmium had no statistically significant effect on mortality and mean survival time following primary or secondary challenge with any of the infectious agents. However, there was a dose-related, increased susceptibility to Herpes simplex type 2 virus. T- and B-lymphocyte proliferation was significantly reduced, and macrophage phagocytosis was significantly increased following cadmium exposure. NK cell activity was augmented, but not significantly. Macrophage bactericidal activity and DTH were not significantly altered.

Effect of mercurials on lymphocyte functions in vitro

The effect of in vitro treatment with mercurials on several functions of mouse lymphocytes was studied. When lymphocytes were cultured in the presence of mercurials, DNA synthesis induced by mitogen (concanavalin A, phytohemagglutinin-P, lipopolysaccharide) and polyclonal B cell activation induced by lipopolysaccharide were strongly inhibited by methylmercuric chloride at the concentration of 10(-6) M, but mercuric chloride inhibited these functions by 50% at 10(-5) M. Furthermore, 10(-7) M methylmercuric chloride and 10(-6) M mercuric chloride inhibited mixed lymphocyte reaction by 80%. Thus, the inhibitory effect of methylmercuric chloride was 10 times stronger than that of mercuric chloride when the mercurials were present in the culture throughout the incubation. On the other hand, DNA synthesis once induced by mitogens was not significantly affected when 10(-6) M methylmercury was added during the last 3 h of the incubation. Pretreatment with 10(-6) M methylmercury for 1 h, however, showed 50% inhibition of thymidine incorporation into DNA and also reduced the rate of metabolism of phosphatidyl inositol by 50%. These results indicate that methylmercury may act on mouse lymphocytes at an early stage of transformation induced by the mitogens, while inorganic mercury failed to cause the pronounced difference in its potency of inhibition on the functions of lymphocytes by the different treatments of the cells under the various conditions used.

Low level chromium (VI) inhalation effects on alveolar macrophages and immune functions in Wistar rats

In inhalation chambers, 5-week-old male Wistar rats of the strain TNO-W-74 were continuously exposed to submicron aerosols of sodium dichromate in concentrations from 25 (low level) to 200 micrograms/m3 Cr (high level). Subacute exposure (28 days) to 25 and 50 micrograms/m3 Cr resulted in "activated" alveolar macrophages with stimulated phagocytic activities, and significantly elevated antibody responses to injected SRBC's. After subchronic (90 days) low level exposure there was a more pronounced effect on activation of the alveolar macrophages, with increased phagocytic activities. However, at high Cr (VI) exposure level (200 microgram/m3), inhibited phagocytic function of the alveolar macrophages was seen. In rats which were exposed to this chromium aerosol concentration for 42 days, the lung clearance of inert iron oxide was reduced significantly. The humoral immune system was still stimulated at subchronic low chromium aerosol concentrations of 100 micrograms/m3, but significantly depressed at 200 micrograms/m3 Cr. These results show that respiratory defence and immunologic functions were stimulated or inhibited depending on dose and time of chromium (VI) inhalation.

In vitro effect of cadmium on primary antibody response to T-cell independent antigen (DNP-Ficoll)

The effect of various concentrations of cadmium on the in vitro primary antibody response to T-cell independent antigen (DNP-Ficoll) was investigated. Anti DNP-Ficoll antibody response in mice was significantly enhanced by 8 microM cadmium, but suppressed by 20 and 40 microM cadmium. However, cell viabilities were decreased by cadmium exposure with dose-dependent relationships. The results suggest that in vitro exposure to cadmium produces different effects on antibody responses.

Effects of NiO inhalation on alveolar macrophages and the humoral immune systems of rats

To study the effects of inhaled NiO particles on alveolar macrophages and the humoral immune system, male Wistar rats were continuously exposed to NiO aerosols for 4 weeks and 4 months, respectively. Fractions of alveolar macrophages, granulocytes, and lymphocytes in lung lavages, number of polynucleated macrophages, size of macrophages, and phagocytic activity were determined. To test the effects on the humoral immune response sheep erythrocytes were injected, and the antiserum titer in blood and the portion of antibody forming cells in spleen were measured. Significant alterations were found in both systems at 100 and 200 micrograms Ni/m3 after 4 weeks of exposure and at 25 and 150 micrograms Ni/m3 after 4 months of exposure, respectively. The results demonstrate the usefulness of investigations on the humoral immune system and alveolar macrophages as sensitive parameters in detecting effects of NiO inhalation.

Natural and acquired resistance of mice to infection by airborne Klebsiella pneumoniae after subchronic intoxication by cadmium administered orally

Mice daily ingested about 22 mg of cadmium per kg of body weight in drinking water for 30 days. On the 30th day, the liver and kidneys of the mice contained about 18 micrograms of Cd2+ per g of fresh organ. A group of these mice was immunized against Klebsiella pneumoniae using two injections of vaccine, the first on the 7th day and the second on the 14th day of intoxication. On the 28th day, the non-immunized and the immunized mice were infected via a respiratory route by one lethal dose 50% of K. pneumoniae (the LD50 for the immunized mice was 2.4 times higher than the LD50 for the non-immunized mice). Comparison with the non-intoxicated control mice showed that the ingestion of Cd2+ did not significantly modify the natural resistance or the acquired resistance of the mice to the infection by airborne K. pneumoniae.

Altered immune response during cadmium administration in mice

C57BL/6 mice were administered 50 or 200 ppm of Cd as CdCl2 in the drinking water for either 3 to 4 (short term) or 9 to 11 (long term) weeks. In other experimental designs, mice were exposed orally to 300 ppm of Cd or injected with 2.5 mg/kg of Cd ip. The proliferative response to the T cell mitogens Con A and PHA was increased in cultures of spleen cells from orally treated mice in most of the experiments performed. After primary immunization with sheep red blood cells, the number of IgM antibody forming cells per 10(7) spleen cells was also moderately higher in mice exposed to 50 or 200 ppm of Cd for short or long term. In contrast, long-term exposure to 300 ppm of Cd depressed the antibody response to SRBC. Administration of ZnCl2 prevented the enhancement of the PFC response in mice orally administered 50 ppm of Cd. The capacity to suppress the antibody response of spleen cells preincubated with sodium periodate was decreased after short-term oral or ip. Cd administration but was completely or partially recovered after long-term exposure to either 50 or 200 ppm of Cd.

Biochemical and hematological studies on perch, Perca fluviatilis, from the cadmium-contaminated river Emån

In a field investigation, biochemical and hematological parameters were measured in perch, Perca fluviatilis, living in the cadmium-contaminated river Emån in the southeast of Sweden. The number of lymphocytes was 45-100% higher in perch from the contaminated area than in the reference perch, indicating a stimulated immune defense. In addition, the cadmium-loaded fish suffered from a slight anemia and a disturbed carbohydrate metabolism and blood plasma ion composition. The observed effects suggest that cadmium affects fish in the environment similar to what has been observed in laboratory studied. However, the weaker response may imply that the perch in the field stimulation have been adapted and thus acquired an increased resistance to cadmium.

Effects of single exposure to cadmium on the primary humoral antibody response

Effects of a single intraperitoneal (i.p.) injection of cadmium (Cd) on the primary humoral antibody responses against sheep red blood cells (SRBC) in mice were studied by assaying splenic plaque forming cells (PFC). PFC responses in mice were suppressed when exposed to Cd 2 days after immunization, and inconsistently stimulated when exposed before immunization. Dose-response relationships were observed in the suppressive effect of Cd exposure 2 days after immunization, but not consistently in the stimulative effect of Cd exposure before immunization. Thymus weights and cell numbers decreased markedly 4 days after Cd exposure with or without the antigenic stimulus. Splenic weights increased 2 days after Cd exposure, while the number of spleen cells was dramatically decreased 1 days after Cd exposure and still remained below normal 2 days after exposure.

Inhibition of delayed hypersensitivity reaction in mice by cadmium

The effect of a single exposure to Cd on DH was studied through exposure to Cd at different time intervals in relation to antigen administration. Exposure to Cd significantly suppressed the DH reaction, with a dose-response relationship, when administered 2 or 3 days after immunization of BALB/c and DBA/2 mice with sheep red blood cells. A strain difference in sensitivity to Cd was also demonstrated. These results suggest that a single exposure to Cd impairs the cellular immune response in mice.

Cadmium-induced suppression of the primary immune response and acute toxicity in mice: differential interaction of zinc

Four groups of 6-week-old C3H mice were injected sc with either sterile saline, 2.8 mg Cd/kg body weight, 2.8 mg Zn/kg body weight, or 2.8 mg each of Cd and Zn/kg body weight. Forty-eight hours after the initial injection, all mice received a second dose of their respective treatments plus an iv injection of sheep red blood cells. On Days 2, 3, 4, and 5 postimmunization the mice were killed. Spleen cells were used in a hemolytic plaque-forming assay for the quantitation of the primary humoral response. Although the combined administration of zinc and cadmium completely prevented the fatal effects of the cadmium (0 vs 55% mortality), zinc failed to alleviate the cadmium-induced inhibition of the humoral response.

Modified distribution of lymphocyte subpopulation in blood and spleen from mice exposed to cadmium

The effect of cadmium (Cd) on the lymphocyte subpopulation in peripheral blood and spleen was studied in ICR mice given a daily subcutaneous injection of 0.5 and 1.0 mg Cd/kg body weight for 5 days or mice fed with the drinking water containing 3, 30 and 300 ppm Cd for 10 weeks. The reduction of blood B lymphocytes observed in Cd-injected mice was accompanied by the increase of the number of splenic B lymphocytes. On the other hand in Cd-fed mice the reduction of blood T lymphocytes was found and associated with the increase of the number of splenic T lymphocytes. These findings suggest that circulating lymphocytes may redistribute differentially in lymphoid organs responded to the Cd exposure.

Effect of cadmium on the immune response in rats

Adult male inbred Wistar rats were given a subtoxic dose of cadmium (25 ppm) orally for 4 weeks prior to and during immunization with sheep erythrocytes (E). The control group received tap water during the experimental period. No difference in the antibody response to E was found between the two groups. Mononuclear peripheral blood cells from experimental and control rats were stimulated with concanavalin A (Con A). The experimental rats had received 25 ppm Cd in the drinking water from weaning until sacrifice at 15 weeks of age. There was no difference in [3H]thymidine incorporation between the cells of the experimental group and those of the control group. Addition of Cd at very low concentrations to the cultures significantly depressed the [3H]thymidine incorporation of the cells from both groups of rats. Thus, a subtoxic dose of Cd apparently had no effect on the in vivo immune response in rats.

Cadmium-induced immunotoxicity

This study assessed the effects of cadmium on functional lymphopoietic precursor cells and cell size in both spleen and bone marrow. Splenic plaque-forming cell (S-PFC) precursors were stimulated by a thymus independent immunogen (TNP-LPS) and by a thymus dependent immunogen (TNP-BSA plus dextran sulfate). Bone marrow plaque-forming cell (M-PFC) precursors were stimulated by TNP-LPS plus dextran sulfate. Male C57Bl/6J mice received either a single ip injection of 5.9 mg/kg CdCl2, and were sacrificed 3 days later (ip group), or 5 daily sc injections of 3.26 mg/kg CdCl2, and were sacrificed either 2 days later (7 day sc group) or 7 days later (12 day sc group). The ip group showed an increase in spleen cellularity which resulted in an enhanced S-PFC (TNP-LPS) response per spleen and compensated for a depressed S-PFC (TNP-BSA) response per 10(6) cells cultured. Bone marrow cellularity was not significantly decreased but the M-PFC response was drastically depressed. Similar results were obtained in the 7 day sc group. However, a significant increase in spleen cellularity was not seen, resulting in a noncompensated decrease in S-PFC (TNP-BSA) response. The S-PFC (TNP-LPS) response per 10(6) cells cultured was increased in this group. Responses were similar to controls in the 12 day sc group, but bone marrow cellularity was decreased. The ip and 7 day sc groups showed substantial cadmium-induced shifts in bone marrow cell size distribution profile to larger diameters. Changes in spleen cell size distribution were not as significant. Partial recovery was evident in the 12 day sc group. This study demonstrated that in vivo exposure to cadmium has a greater effect on the in vitro function of immature B-cells in the bone marrow than on more mature B-cells found in the spleen.(ABSTRACT TRUNCATED AT 250 WORDS)

Strain variations in cadmium-induced suppression of lymphocyte transformation in mice

Cadmium is an environmental pollutant which has been shown in numerous studies to significantly affect immune responses. However, a review of the literature reveals many inconsistencies, both qualitative and quantitative, in the effects of cadmium on the immune system. In the present study, we examine the influence of genetic background on the effects of cadmium using lymphocyte transformation as an index of immunocompetence. Cadmium was added in vitro to mitogen and non-mitogen stimulated splenocyte cultures obtained from Balb/c, C57BL and C3HeB mice. Cadmium, 1-30 microM, was associated with a dose-dependent, linear inhibition of lymphocyte transformation in all strains. In unstimulated and Con A-stimulated cultures, the cadmium-inhibition plots were parallel but non-coincident in the three strains of mice with C57 being the most susceptible and C3H the most resistant to the inhibitory effects of cadmium. For LPS-stimulated lymphocyte transformation, the cadmium inhibition plots had different slopes in the three strains of mice suggesting a possible difference in the mechanism of action of cadmium. The relationship between these findings and cadmium-induced cytotoxicity as well as metallothionein synthesis are discussed.

Modification of skin-graft rejection and acceptance by low concentrations of cadmium in drinking water of mice

Skin allograft rejection and isograft acceptance was studied in Balb/c mice exposed to 0, 0.01, 0.1, 1.0, or 10.0 ppm cadmium in drinking water beginning 4 wk prior to grafting. Cadmium exposure was associated with a dose-dependent acceleration of the rejection of allografts prepared from the tail skin of C57/BL mice. The mean time to allograft rejection decreased from 10.4 d in non-metal-exposed recipients to 7.4 d in mice exposed to 10 ppm cadmium. Cadmium exposure was also associated with a dose-dependent increase in the time to isograft acceptance (8.6 d in control mice compared to 11.0 d in mice exposed to 10 ppm cadmium). In addition, some isografts were rejected by animals exposed to 1 or 10 ppm cadmium. It is suggested that a cadmium-induced modification of the wound-healing process could explain both the allograft and isograft response, although an effect of cadmium on the immune response to histoincompatible tissue may also play a role in the accelerated allograft rejection.

Acute effects of cadmium on delayed-type hypersensitivity in mice

A single exposure of mice to cadmium resulted in suppression of the induction of primary delayed-type hypersensitivity (DTH) responses as well as memory T-cell and suppressor T-cell activities, augmenting and inhibiting DTH respectively. Furthermore, cadmium suppressed the expression of already established DTH, in immune mice, even though DTH-effector T cells in the spleen of immune mice were not affected by cadmium injection. Such suppressive effects were demonstrated when cadmium was administered within 2 days before immunization or elicitation for DTH. Cadmium caused also within 2 days in mice thymic involution and splenomegaly. These results indicate that cadmium inhibits not only the generation of certain populations of T lymphocytes for DTH but also some mechanisms in the host involved in the expression of DTH.

Thymic atrophy in mice induced by cadmium administration

The effects of cadmium (Cd) on the immune organs were examined histopathologically. On 2 or 3 days after a single i.p. injection of 1.8 mg Cd/kg body weight into mice, slight loss of body weight, significant decrease of thymus weight and marked increase of spleen weight were observed. Lymph node weight did not show any change. Histopathologically, cortical atrophy of the thymus was very marked. The white pulp of the spleen tended to diminish in size any many polymorphonuclear leukocytes and myeloid cells appeared in the red pulp.