Evaluation of the potential immunotoxicity of bromodichloromethane in rats and mice

In the past two decades, concern has been expressed over the potential carcinogenicity of disinfection by-products (DBPs) found in chlorinated drinking water. More recently, research efforts have expanded to include noncancer endpoints as well. The objective of the present studies was to evaluate the potential of bromodichloromethane (BDCM), one of the most prevalent DBPs, to adversely affect immune function in mice and rats following drinking water or gavage exposure. Antigen-specific immunity was assessed as the antibody response to sheep erythrocytes; responses to T- and B-cell mitogens were evaluated as a non-antigen-specific measure of the proliferative potential of splenic and mesenteric lymph node lymphocytes. In consideration of an exposure route relevant to humans, C57BL/6 mice received 0.05, 0.25, or 0.5 g BDCM/L and F344 rats received 0.07 or 0.7 g BDCM/L via drinking water. In order to evaluate the effects of higher doses, animals were administered 50, 125, or 250 mg BDCM/kg/d (mice) or 75, 150, or 300 mg BDCM/kg/d (rats) via gavage. Under the conditions of these studies, no significant adverse effects on immune function were observed in mice. Despite some changes that were observed in non-antigen-specific immunity in rats, these experiments suggest that the immune system is not a sensitive target organ for BDCM toxicity.

Evaluation of the potential immunotoxicity of chlorinated drinking water in mice

Recent epidemiological studies have reported associations between the consumption of chlorinated drinking water and various types of human cancer; in addition, exposure to chlorine (Cl-) in drinking water has been reported to suppress certain immune functions in laboratory animals. The current studies were conducted to extend our knowledge of the effects of drinking water exposure to Cl-. Female C57BL/6 mice were administered hyperchlorinated drinking water (7.5, 15, or 30 ppm Cl-) for 2 weeks prior to sacrifice for evaluation of spleen and thymus weights, the plaque-forming cell (PFC) response, hemagglutination (HA) titer, and lymphocyte proliferation (LP). Significant reductions in organ weights and immune response were observed in the positive control groups (i.e. dexamethasone- or cyclophosphamide-exposed mice). No consistent differences were observed between the Cl--exposed animals and vehicle control mice for the evaluated parameters. Thus, under the conditions of these experiments, 2 weeks of exposure to hyperchlorinated drinking water had no apparent adverse effects on immune function.

Alterations in the developing immune system of the F344 rat after perinatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin: II. Effects on the pup and the adult

Our recent work showed that in utero 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure produced alterations in fetal and neonatal thymocyte subpopulations. This study was designed to determine the persistence and functional significance of these alterations. One group of timed-bred pregnant F344 rats was dosed with 3.0 mcg TCDD/kg by gavage on gestational day 14 (GD14). The immune function of the perinatally-exposed offspring and age-matched controls were assessed at 14-17 weeks old. Examination of the organ weights and splenic phenotypes showed that TCDD exposure increased the spleen/body weight ratio, decreased the thymus/body weight ratio, and decreased the percentage of splenic CD3+/CD4-CD8- cells in both genders. The delayed-type hypersensitivity (DTH) response to bovine serum albumin (BSA) was suppressed in both the TCDD-exposed males and females. The lymphoproliferative (LP) responses to T-cell and B-cell mitogens and the antibody response to sheep red blood cells were not affected by perinatal TCDD exposure in either gender except for a suppressed LP response to PWM in the females. A second set of timed-pregnant F344 rats was dosed with 0 or 1.0 mcg TCDD/kg on GD14. One day after birth litters were cross-fostered to produce control, placental-only, lactational-only, and placental/lactational exposure groups. The organ weights and thymic and splenic phenotypes of these pups were assayed 1, 2, or 3 weeks post-partum, while the DTH response was assessed in 5-month-old males. Increased liver/body weight ratios, decreased percentages of thymic CD3+/CD4-CD8- cells, and increased percentages of thymic CD3+/CD4-CD8+ cells were seen through 3 weeks old in both genders after TCDD exposure. The severity of the effects was related to the route of exposure (i.e. placental/lactational > lactational > placental). The DTH response to BSA was suppressed in the males receiving both placental and lactational exposure. These results suggest that the immunotoxic effects of perinatal TCDD exposure of rats persist into adulthood and that suppression of the DTH response may represent the most sensitive biomarker for TCDD-induced immunotoxicity in this species.

Rapid recovery management: the effects on the patient who has undergone heart surgery

OBJECTIVE

To determine whether patients who have undergone heart surgery can be managed with use of rapid recovery guidelines without any subsequent increase in complication, mortality, or readmission rates.

DESIGN

Retrospective study, two groups, comparative.

SETTING

Private midwestern hospital with 690 licensed beds.

SUBJECTS

Group I consisted of 312 adult patients who had undergone heart surgery in 1993 who were managed using traditional methods. Group II consisted of 303 patients who had undergone heart surgery in 1994 who were managed using rapid recovery guidelines.

OUTCOME MEASURES

Complications (pneumonia and wound infections), mortality, and readmission rates.

RESULTS

Of the surgeries performed in 1994, 44% of the patients were discharged by postoperative day 4. No increase was noted in complication, mortality, and readmission rates.

CONCLUSIONS

When compared to patients who were managed by traditional methods, these findings indicated that it is possible to manage adult patients who have undergone heart surgery using rapid recovery guidelines and maintain high-quality patient outcomes and level of satisfaction. In addition, cost savings and decreased resource use are added benefits.

Opposite effects of 2,2',4,4',5,5'-hexachlorobiphenyl and 2,3,7,8-tetrachlorodibenzo-p-dioxin on the antibody response to sheep erythrocytes in mice

The effect that cotreatment with 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has on the antibody plaque-forming cell (PFC) response to sheep red blood cells (SRBCs) was determined in female B6C3F1 mice. Groups of eight mice per group were given a single oral dose of PCB153 alone (0, 3.58, 35.8, or 358 mg/kg), TCDD alone (0, 0.1, 1, or 10 micrograms/kg), and all possible combinations of these doses in corn oil 7 days prior to immunization with SRBCs. Separate groups of mice were given phenobarbital (PB) parenterally by intraperitoneal injection at a dosage of 160 mg/kg/day for 3 days. Four days after intravenous immunization, body, spleen, thymus, and liver weights and the PFC response to SRBCs were determined. Exposure to TCDD alone resulted in a dose-related suppression of the PFC response, with significant suppression at 1 and 10 micrograms/kg. In contrast, exposure to PCB153 alone resulted in the enhancement of the PFC response at 358 mg/kg. Combined exposure to 358 mg/ kg PCB153 and TCDD resulted in no change (PCB153 + 0.1 microgram/ kg TCDD) or suppression (PCB153 + 1 or 10 micrograms/kg TCDD) of the PFC response relative to PCB153 alone; however, the PFC response was enhanced (PCB153 + 0.1 microgram/kg TCDD), unaffected (PCB153 + 1 microgram/kg TCDD), or suppressed (PCB153 + 10 micrograms/kg TCDD) relative to corn oil controls. PB did not affect the PFC response to SRBCs, despite a 13-fold induction of hepatic pentoxyresorufin O-dealkylase (PROD) activity. These results suggest that PCB153 enhancement of the PFC response is not related to PROD induction and that it acts as a functional antagonist rather than an aryl hydrocarbon receptor or dispositional antagonist. By enhancing the PFC response to SRBCs, PCB153 raises the "setpoint" response level. Consequently, cotreatment with an immunosuppressive dose of TCDD fails to suppress the PFC response relative to corn oil controls, while clearly suppressing it relative to the appropriate control, PCB153 alone.

Comparison of the T cell-independent antibody response of mice and rats exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant that produces adverse effects on the immune system of experimental animals. In this study, the effect that TCDD has on the antibody plaque-forming cell (PFC) response to the T cell-independent (TI) antigen trinitrophenyl-lipopolysaccharide (TNP-LPS) was compared in adult female B6C3F1 mice and F344 rats. Mice or rats were given a single intraperitoneal injection of TCDD at doses ranging from 1 to 30 micrograms/kg, 7 days prior to immunization with TNP-LPS by intravenous injection. Three days later body, spleen, thymus, and liver weights were measured and the PFC response to TNP-LPS was determined. Thymus weights were decreased at 10 and 30 micrograms TCDD/kg, whereas spleen weights were decreased and liver weights increased in mice dosed at 3, 10, and 30 micrograms/kg. Mice dosed at 10 and 30 micrograms TCDD/kg had suppressed PFC responses and serum hemagglutination titers. In rats, thymus weights were decreased and liver weights increased at 3, 10, and 30 micrograms TCDD/kg; however, the PFC response and serum hemagglutination titers to TNP-LPS were suppressed only at 30 micrograms/kg TCDD. TCDD did not affect splenic lymphocyte subsets evaluated by flow cytometry. These results indicate that TCDD suppresses the TI antibody response to TNP-LPS in both B6C3F1 mice and F344 rats, with mice more sensitive to suppression by TCDD than rats.

Repeated high dose oral exposure or continuous subcutaneous infusion of 2-methoxyacetic acid does not suppress humoral immunity in the mouse

2-Methoxyethanol (ME) has been shown to be immunosuppressive in rats but not mice, with oxidation of ME to 2-methoxyacetic acid (MAA) being a prerequisite for immunosuppression. MAA is more rapidly cleared by mice than rats, consequently this study was designed to determine if increasing the bioavailability of MAA in mice might play a role in this species difference. Female B6C3F1 mice were given MAA by oral multiple daily high doses or by continuous subcutaneous infusion via mini-osmotic pumps. Humoral immunity was evaluated in MAA-exposed mice using the plaque-forming cell (PFC) response to either sheep red blood cells (SRBC) or trinitrophenyl-lipopolysaccharide (TNP-LPS). Female F344 rats were also used to compare the effects of multiple daily MAA exposure on these humoral immune responses. Rats and mice were dosed orally twice a day for 4 days by gavage with MAA at dosages ranging from 40-320 mg/kg/day and 240-1920 mg/kg/day, respectively. All animals were immunized on the first day of dosing and body and lymphoid organ weights and PFC responses to SRBC or TNP-LPS were evaluated 4 days later. While body weights in rats were unaffected, thymus weights were reduced at all dosages of MAA and spleen weights were reduced at 160 or 320 mg/kg/day. PFC responses to SRBC and TNP-LPS were suppressed in rats at dosages of 160 and 320 mg/kg/day. In contrast, thymus weights of mice were reduced only at 960 mg/kg/day or greater, with no effect on spleen or body weights. Furthermore, neither the PFC response to SRBC nor the response to TNP-LPS was suppressed in mice exposed to any oral dosage of MAA. In the continuous infusion study, mice were subcutaneously implanted with mini-osmotic pumps containing MAA which was delivered at 840 mg/kg/day over a 7-day period. Continuous exposure to MAA via mini-osmotic pumps did not suppress the PFC response to either SRBC or TNP-LPS, but rather significantly enhanced the response to TNP-LPS. These results indicate that mice are insensitive to MAA even at the high dosages given as a bolus or continuously over 1 week. The data further support earlier work, which suggested that the observed difference between rats and mice for MAA-induced immunosuppression appears to be unrelated to the availability of MAA to target lymphoid tissue in these rodent species.

A rapid recovery program for cardiac surgery patients

Despite a strong national commitment to excellence in healthcare, the available resources are limited. Cardiac surgery consumes more healthcare resources than any other single treatment. It is imperative that healthcare professionals evaluate the traditional methods used to deliver quality care. Rapid recovery programs have been implemented in response to this challenge. The purpose of this article is to discuss development, implementation, and outcome evaluation of a rapid recovery program for cardiac surgery patients in a single health center. A multidisciplinary team examined care before, during, and after surgery, as well as after discharge. The team also evaluated standards of care and CARE Pathways. Changes in protocols were made to prevent the predictable complications of cardiac surgery. A decrease in intubation time, respiratory infections, wound infections, laboratory procedures, length of stay, and costs has been demonstrated. In a follow-up patient and family survey, high satisfaction with nursing care, patient and family education, and length of hospitalization has been voiced. Anticipated goals have been exceeded and improvements in standards continue to be made.

A rapid recovery program for cardiac surgery patients

Despite a strong national commitment to excellence in healthcare, the available resources are limited. Cardiac surgery consumes more healthcare resources than any other single treatment. It is imperative that healthcare professionals evaluate the traditional methods used to deliver quality care. Rapid recovery programs have been implemented in response to this challenge. The purpose of this article is to discuss development, implementation, and outcome evaluation of a rapid recovery program for cardiac surgery patients in a single health center. A multidisciplinary team examined care before, during, and after surgery, as well as after discharge. The team also evaluated standards of care and CARE Pathways. Changes in protocols were made to prevent the predictable complications of cardiac surgery. A decrease in intubation time, respiratory infections, wound infections, laboratory procedures, length of stay, and costs has been demonstrated. In a follow-up patient and family survey, high satisfaction with nursing care, patient and family education, and length of hospitalization has been voiced. Anticipated goals have been exceeded and improvements in standards continue to be made.

Immunological effects of 2-methoxyethanol administered dermally or orally to Fischer 344 rats

Exposure of rats to 2-methoxyethanol (ME) by gavage for 10 consecutive days results in immunotoxicity. To determine whether dermal exposure to ME also induces immunotoxicity, undiluted ME was applied to Fisher 344 male rats at dose levels of 150, 300, 600, 900 or 1200 mg/kg/day on shaved occluded test sites for 4 consecutive days. Decreased thymus weights were produced by all doses of ME, while reductions in spleen weight were observed at doses of 900 mg/kg/day ME or greater. The alterations in these lymphoid organ weights were produced in the absence of loss in body weight. The lymphoproliferative (LP) responses to phytohemagglutinin (PHA) and pokeweed mitogen (PWM) were enhanced at 1200 mg/kg/day ME compared with water controls. Separate groups of rats, employed for the antibody plaque-forming cell (PFC) response to either trinitrophenyl-lipopolysaccharide (TNP-LPS) or sheep red blood cells (SRBC), were exposed dermally to 150, 300 or 600 mg/kg/day ME for 4 consecutive days. A reduction in the PFC response to TNP was observed at 600 mg/kg/day ME, whereas decreases in the PFC response to SRBC were observed at dosages of 300 and 600 mg/kg/day ME. To compare the immunotoxic effects of dermally applied ME to those effects caused by ME administered orally, rats were dosed by gavage with 25, 50, 100 or 200 mg/kg/day ME in distilled water for 4 consecutive days. Reductions in thymus weights were observed at oral dosages ranging from 50-200 mg/kg/day, while spleen weights were reduced in rats dosed at 200 mg/kg/day ME. LP responses to PHA, PWM and Salmonella typhimurium were increased at the 200 mg/kg/day ME dose level. PFC responses to TNP-LPS and SRBC were suppressed at the 50, 100 and 200 mg/kg/day ME dosages. These results indicate that, like oral exposure, dermal exposure to ME compromises the ability of the immune system to mount an effective humoral immune response.

Species and strain comparisons of immunosuppression by 2-methoxyethanol and 2-methoxyacetic acid

2-Methoxyethanol (ME) and its principal metabolite 2-methoxyacetic acid (MAA) have been shown in our laboratory to be immunosuppressive in male Fischer 344 rats. In this study several strains of 12-week-old female rats and mice were used to compare the immunosuppressive activity of equimolar concentrations of ME and MAA on the trinitrophenyl-lipopolysaccharide (TNP-LPS) antibody plaque-forming cell (PFC) response, which we previously demonstrated to be a sensitive end point. Female inbred Lewis, Fischer 344 and Wistar/Furth, and outbred Sprague-Dawley rats were dosed by gavage with either ME or MAA at dosages of 0.33 to 2.64 mmol/kg/day for 10 consecutive days. Female inbred C3H and C57BL/6J, hybrid B6C3F1, and outbred CD-1 mice were similarly dosed with equimolar dosages of 0.66 to 5.28 mmol/kg/day ME or MAA. All animals were immunized on day 9 of dosing and PFC responses evaluated 3 days later. Suppression of the PFC response was observed in all strains of rats at 2.64 mmol/kg/day ME or MAA. Lewis and Wistar/Furth rats were found to be the most sensitive strains with suppression at levels as low as 0.66 mmol/kg/day ME or MAA. While ME and MAA dosing resulted in suppression of the TNP PFC response in all the rat strains tested, such treatment did not suppress this PFC response in any of the mouse strains examined. These results indicate that under the conditions of this study rats, but not mice, are immunosuppressed by ME and MAA exposure, and that the susceptibility to immunosuppression differs among rat strains.

Assessment of host resistance to Trichinella spiralis in mice following preinfection exposure to 2,3,7,8-TCDD

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been reported to decrease host resistance to a variety of infectious agents when exposure occurs prior to infection. Resistance to viral infection has been observed at doses as low as 0.1 microgram TCDD/kg body wt, well below the thymolytic dose in mice. In the present study, female B6C3F1 mice were exposed to a single intraperitoneal injection of 0, 0.1, 1.0, 10.0, or 30.0 micrograms TCDD/kg 7 days prior to infection to determine the effects of TCDD exposure on resistance to the nematode parasite Trichinella spiralis. Exposure to 10 or 30 micrograms TCDD/kg delayed adult parasite elimination from the small intestine. Significantly more larvae were released by female parasites and greater numbers of encysted larvae were recovered from the muscle of mice exposed to TCDD. Proliferative responses of splenocytes and mesenteric lymph node cells stimulated with T. spiralis antigen were significantly suppressed at exposure levels of TCDD > or = 1.0 microgram/kg 7 days after infection and in splenocytes only at 14 days after infection, demonstrating the greater sensitivity of proliferative responses to TCDD exposure than actual host resistance to Ts infection. Suppressed proliferation was observed at doses which produced TCDD concentrations > or = 0.2 pmol/g of lymphoid tissue on Day 7 of infection. In addition, it was determined that infected mice had higher TCDD levels than noninfected mice given the same dose. These results suggest an interaction between TCDD exposure and infection, i.e., that exposure to TCDD altered the host response to infection, while infection delayed elimination of TCDD from the host.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on humoral immunity and lymphocyte subpopulations: differences between mice and rats

While the effect that TCDD has on humoral immunity has been well documented for the mouse, it has not been for the rat. In this study, the effect that TCDD has on the antibody plaque-forming cell (PFC) response to sheep red blood cells (SRBC) in adult female B6C3F1 mice and F344 rats was compared. The effect that TCDD has on the PFC response of male F344 and female Long-Evans rats was also determined. Mice or rats were given a single intraperitoneal injection of TCDD at doses ranging from 0.1 to 30 micrograms/kg, 7 days prior to intravenous immunization with SRBC. Four days later the PFC response to SRBC was determined. Mice showed a dose-related suppression of the PFC response, with an ED50 of 0.7 micrograms/kg TCDD. In contrast, TCDD failed to suppress and in fact enhanced the PFC response to SRBC in rats at doses as high as 30 micrograms/kg. The inability of TCDD to suppress the PFC response in rats was unrelated to hepatic CYP1A1 and CYP1A2 induction which was detectable at doses of 1 and 0.3 microgram/kg TCDD, respectively. There was no shift in the time to peak PFC response in rats dosed with TCDD, nor was the failure of TCDD to suppress the PFC response in rats related to gender or strain. Phenotypic analysis of thymocytes and splenic lymphocytes from TCDD-dosed (i.e., 3, 10, or 30 micrograms/kg) and SRBC-immunized mice and rats revealed that CD4-CD8+ splenocytes were reduced in a dose-related manner in rats only and that this reduction in CD4-CD8+ was accompanied by a dose-related increase in IgM+ splenocytes. These results demonstrate species differences in the effect of TCDD on the PFC response to SRBC which were unrelated to hepatic CYP1A1 or CYP1A2 induction, time to peak response, gender, and strain. The failure of TCDD to suppress and in fact to enhance the PFC response to SRBC in rats appears to be related to alterations in splenic CD4-CD8+ lymphocytes.

Methoxyacetaldehyde, an intermediate metabolite of 2-methoxyethanol, is immunosuppressive in the rat

2-Methoxyethanol (ME) is metabolized to 2-methoxyacetic acid (MAA) via the intermediate metabolite methoxyacetaldehyde (MAAD). Both ME and MAA have been shown in this laboratory to be immunosuppressive in rats following oral dosing. In this study, the plaque-forming cell (PFC) response to trinitrophenyl-lipopolysaccharide (TNP-LPS) was used to determine if MAAD is immunosuppressive in rats. Rats pretreated with the aldehyde dehydrogenase inhibitors disulfiram (2 mmol/kg) or cyanamide (0.48 mmol/kg) followed by oral dosing with ME (2.64 mmol/kg) resulted in suppressed PFC responses equivalent to the suppressed responses of rats dosed with ME alone. Rats pretreated with disulfiram and then dosed with 2.64 mmol/kg 2-methoxyethyl acetate (MEA), also resulted in suppressed PFC responses similar to that of MEA alone. In contrast, coadministration of the alcohol dehydrogenase inhibitor 4-methylpyrazole (1.2 mmol/kg) with ME or MEA blocked suppression of the PFC response following exposure to ME or MEA alone. Oral dosing with equimolar (2.64 mmol/kg) concentrations of ME, MAA, or MAAD resulted in equivalent suppression of the TNP-LPS PFC response. Rats exposed to either disulfiram or cyanamide and MAAD also resulted in suppression of the PFC response. These results indicate that metabolism of ME to either MAAD or MAA is required for immunosuppression, and that these two metabolites are equipotent immunosuppressants in the rat.

Assessment of the immunotoxic potential of the fungicide dinocap in mice

The immunotoxic potential of dinocap was evaluated in female C57BL/6J mice following in vivo and in vitro exposure to this fungicide. In in vivo studies, groups of mice were dosed by gavage with technical grade dinocap at dosages ranging from 12.5 to 50 mg/kg per day for 7 or 12 days and selected immune functions examined. Mice dosed at 50 mg/kg per day dinocap died after 4 days of dosing. Twelve days of dosing with dinocap at 25 mg/kg per day resulted in decreased thymus weights and cellularity, and increased spleen weights. No changes were observed in body weight, absolute differential peripheral leukocyte counts, the lymphoproliferative responses to B- or T-cell mitogens, the mixed lymphocyte reaction, or natural killer (NK) cell activity of spleen cells from mice exposed to dinocap. Lymphoproliferative responses to concanavalin A (Con A) and phytohemagglutinin (PHA), however, were reduced in thymocytes from mice dosed at 25 mg/kg per day dinocap. The cytotoxic T lymphocyte (CTL) response to P815 mastocytoma cells was enhanced in mice exposed for 7 days to 25 mg/kg per day dinocap. Exposure of mice for 7 days to 25 mg/kg per day dinocap also caused a significant reduction in the IgM and IgG plaque-forming cell (PFC) response to sheep red blood cells (SRBC). A time-course study indicated that dinocap-induced suppression of the IgM PFC response was due to a delay in the peak PFC response to SRBC. In vitro studies using murine thymocytes cultured with dinocap (10 micrograms/ml for 72 h) resulted in suppression of the proliferative response to Con A and PHA. Exposure of thymocytes to dinocap in vitro for as little as 30 min resulted in suppression of the mitogen-stimulated response in the absence of any apparent direct cytotoxic effect. These results suggest that dinocap alters the immune system of the mouse, however, these effects are relatively modest in terms of adverse immune function and are only seen at relatively high exposure levels.

Differences between rats and mice in the immunosuppressive activity of 2-methoxyethanol and 2-methoxyacetic acid

Previous studies from this laboratory have demonstrated that 2-methoxyethanol (ME) and its principal metabolite 2-methoxyacetic acid (MAA) are immunosuppressive in young adult male Fischer 344 rats. In the present study, the immunosuppressive potential of ME and MAA was evaluated in young adult female Fischer 344 rats and C57BL/6J mice. Rats and mice were dosed by gavage with either ME or MAA in water, at dosages ranging from 50-400 mg/kg/day, for 10 consecutive days. Rats and mice were examined for alterations in body, spleen and thymus weights and mitogen-induced proliferation of splenic lymphocytes in vitro; separate groups were employed for the antibody plaque-forming cell (PFC) response to trinitrophenyl-lipopolysaccharide (TNP-LPS). Rats dosed at 100-400 mg/kg/day ME and rats dosed at 50-400 mg/kg/day MAA had decreased thymus weights in the absence of decreased body or spleen weights. Lymphoproliferative (LP) responses to concanavalin A (Con A), phytohemagglutinin (PHA), pokeweed mitogen (PWM) and Salmonella typhimurium mitogen (STM) were all reduced in rats treated with all dosages of ME. Rats treated with MAA displayed similar reductions in these LP responses except that the responses to PWM and STM in rats dosed at 50 mg/kg/day were not reduced. In contrast to the effects of ME and MAA on these end points in the rat, no thymic involution or suppression of LP responses were observed in mice dosed at 50-400 mg/kg/day. The PFC response to TNP-LPS was suppressed in rats dosed with either ME or MAA at dosages of 100-400 mg/kg/day. ME and MAA, however, failed to suppress the PFC response in mice immunized with TNP-LPS. These results indicate that unlike Fischer 344 rats, C57BL/6J mice are insensitive to the immunosuppressive effects of ME and MAA at the dosages employed in this study. Whether the different sensitivities of these two rodent species to ME- and MAA-induced immunosuppression are due to immunologic, pharmacokinetic or metabolic differences within each species remains to be determined.

Comparative immunosuppression of various glycol ethers orally administered to Fischer 344 rats

Oral dosing of adult male F344 rats with the glycol ether 2-methoxyethanol (ME) or its principal metabolite 2-methoxyacetic acid (MAA) results in the suppression of the primary plaque-forming cell (PFC) response to trinitrophenyl-lipopolysaccharide (TNP-LPS). In the present study, the PFC response to TNP-LPS was used to evaluate the immunotoxic potential of ethylene glycol (EG) as well as the glycol ethers 2-methoxyethyl acetate (MEA), 2-(2-methoxyethoxy) ethanol, bis(2-methoxyethyl) ether, 2-ethoxyethanol and its principal metabolite 2-ethoxyacetic acid, 2-ethoxyethyl acetate, and 2-butoxyethanol relative to ME and MAA. Rats were immunized with TNP-LPS and then exposed 4 and 28 hr later to 50, 100, 200, or 400 mg/kg of glycol ether or EG. Three days following immunization, the PFC response to TNP-LPS was determined. In addition to ME and MAA, only MEA, which was as effective as ME, suppressed the PFC response to TNP-LPS. Concomitant administration of the alcohol dehydrogenase inhibitor 4-methylpyrazole with ME or MEA prevented suppression of the PFC response by these glycol ethers. These results indicate that of the chemicals tested only ME, MEA, and MAA are immunosuppressive, and that oxidative metabolism via alcohol dehydrogenase is necessary for ME- and MEA-suppression of the response to TNP-LPS.

Host resistance to Trichinella spiralis infection in rats and mice: species-dependent effects of cyclophosphamide exposure

Host resistance to Trichinella spiralis infection was compared in male rats (F344) and female mice (C57BL/6J) following various cyclophosphamide (CY) treatment schedules. Doses of CY given to mice were adjusted by body surface area to be comparable to rat doses. Adult parasite elimination was not affected by oral administration of 1.5, 3 or 6 mg CY/kg per day to rats or 1.05, 2.1 or 4.2 mg CY/kg per day to mice for 10 days. In rats, resistance was suppressed by a single oral dose of 80 mg/kg given the day prior to infection, but was not affected at 20 or 40 mg/kg. A single oral dose of 14, 28 or 56 mg CY/kg did not affect parasite expulsion in mice. Rats were also given four daily intraperitoneal (i.p.) injections of 20, 40 or 80 mg CY/kg per day and mice received 14, 28 or 56 mg CY/kg per day. Infected rats did not survive at the two higher dose levels and parasite expulsion was suppressed at 20 mg/kg per day; parasite expulsion was suppressed in mice by four i.p. injections of 56 mg CY/kg per day, but not by lower doses. In rats, doses of CY which suppressed adult parasite expulsion also severely suppressed the proliferative response of mesenteric lymph node cells (MLNC) to an extract of T. spiralis (TsE). However, significant suppression of TsE-driven blastogenesis occurred at a dose of CY which did not affect parasite expulsion, indicating that the proliferative response in rats was more sensitive to suppression than actual parasite elimination. In contrast, the proliferative response to the T cell mitogen concanavalin A was elevated in the MLNC of CY-exposed rats. This was determined to be related to the interval between CY dosing and the day of assay rather than to an effect of infection with T. spiralis. Mouse MLNC proliferative responses to TsE were not suppressed by CY treatment, even at levels of CY which suppressed adult parasite expulsion. Mice differed from rats in that CY exposure did not affect the proliferative response to concanavalin A in infected animals. The species-dependent differences observed in these studies may have been secondary to the greater sensitivity of rats to CY. Nonetheless, these results highlight the potential for species-specific responses to chemical exposure and underscore the need for additional comparative studies of host resistance in rats and mice.

Evaluation of the immunotoxicity of orally administered 2-methoxyacetic acid in Fischer 344 rats

We previously demonstrated that the glycol ether 2-methoxyethanol (ME) is immunotoxic in the rat. In this study, the immunotoxicity of 2-methoxyacetic acid (MAA), the principal metabolite of ME, was evaluated in adult male Fischer 344 rats. Rats were dosed by gavage with MAA on 10 consecutive days at dosages ranging from 50 to 200 mg/kg/day. Thymic involution, in the absence of body weight loss, was observed at 100 and 200 mg/kg/day MAA. Lymphoproliferative responses to the mitogens concanavalin A, phytohemagglutinin, and pokeweed mitogen were also reduced at these dosages. The in vitro generated cytotoxic T lymphocyte response was reduced at 200 mg/kg/day MAA. The mixed lymphocyte reaction and natural killer cell activity were unaffected by exposure to MAA. Enumeration of splenic lymphocyte populations revealed a reduction in the percentage of W3/25-positive cells at 100 and 150 mg/kg/day and an increase in the percentage of OX39-positive cells at 200 mg/kg/day; however, no changes in the absolute number of either of these subsets were observed. The plaque forming cell (PFC) response to trinitrophenyl-lipopolysaccharide (TNP-LPS) was suppressed at 50-200 mg/kg/day MAA, while the PFC response to sheep red blood cells (SRBC) was elevated at 50 mg/kg/day. Immunization of rats with TNP-LPS or SRBC followed by oral exposure to MAA at 4 and 28 hr postimmunization resulted in the suppression of the PFC response to TNP-LPS and SRBC at dosages of 100 and 200 mg/kg and 200 and 400 mg/kg, respectively. Equal suppression of the PFC response to TNP-LPS was achieved at equimolar concentrations of ME and MAA. The effects of MAA on the immune system of the rat presented here are very similar to results reported from this lab for ME-induced immune alterations. These results, along with results of experiments in which ME-induced suppression of the PFC response to TNP-LPS was reversed by 4-methylpyrazole, an inhibitor of the oxidation of ME to MAA by alcohol dehydrogenase, indicate that MAA is the proximate immunotoxicant following exposure to the glycol ether 2-methoxyethanol.

Immunotoxicity of 2-methoxyethanol following oral administration in Fischer 344 rats

The immunotoxicity of the glycol ether 2-methoxyethanol (ME) was evaluated in adult Fischer 344 rats using a variety of in vitro and in vivo immune function assays. In the first phase of this study, male rats were dosed by oral gavage with ME in water, at dosages ranging from 50 to 200 mg/kg/day, for 10 consecutive days. Decreases in thymus weights were observed at dosages of 50-200 mg/kg/day in the absence of decreased body weights. Lymphoproliferative (LP) responses to concanavalin A and phytohemagglutinin were reduced at 50-200 mg/kg/day while pokeweed mitogen and Salmonella typhimurium mitogen responses were reduced at 200 mg/kg/day. No alterations were observed in natural killer cell activity, mixed lymphocyte reaction, or cytotoxic T lymphocyte responses. The frequency of W3/25-positive splenocytes was reduced in rats dosed at 200 mg/kg/day. Interleukin-2 production was reduced in splenocytes from rats exposed to all dosages of ME. The plaque-forming cell (PFC) response to sheep red blood cells was enhanced in rats dosed at 50 mg/kg/day. However, the PFC response to trinitrophenyl-lipopolysaccharide (TNP-LPS) was suppressed at all dosages. Similarly, the PFC response to TNP-LPS was suppressed in adult female rats dosed with ME. A reduction in the expulsion of adult worms was observed in rats dosed at 200 mg/kg/day that were infected with Trichinella spiralis. A number of male reproductive parameters were also evaluated in rats dosed with ME over 10 days. A significant reduction in testicular weight was observed in rats dosed at 200 mg/kg/day. In the second phase of this study, the PFC response to TNP-LPS was employed to assess the role that metabolism of ME to 2-methoxyacetic acid (MAA) plays in the immunotoxicity of this glycol ether. Ten-day oral dosing with MAA resulted in the inhibition of the PFC response to TNP-LPS at dosages of 50-200 mg/kg/day. Concomitant exposure of rats to ME and the alcohol dehydrogenase inhibitor 4-methylpyrazole blocked ME-induced suppression of this PFC response. Attempts to ameliorate ME-induced suppression of the PFC response with serine, which has been shown to reverse ME-induced developmental and reproductive toxicity, were unsuccessful. These results suggest that the immune system may be more sensitive than the reproductive system to the toxic effects of ME. Furthermore, it appears that MAA is the proximate toxicant for ME-induced alterations in the immune system, as has been demonstrated for ME-induced reproductive and developmental toxicity.

Host resistance to murine malaria in mice exposed to the adenosine deaminase inhibitor, 2'-deoxycoformycin

Resistance to infection with the nonlethal rodent malaria parasite Plasmodium yoelii 17XNL (Py 17XNL) is mediated by humoral, T-cell and accessory cell activity. The purpose this study was to profile host resistance to infection with this organism in mice exposed to 2'-deoxycoformycin (2dCF), a potent adenosine deaminase (ADA) inhibitor. Inhibition of ADA activity by 2dFC results in defective T-cell function and either suppression or augmentation of the humoral response, depending on whether 2dCF exposure precedes (suppression) or follows (augmentation) immunization. In this study, mice injected with 2dCF during the first five days of infection cleared the infection at the same time as controls, but had lower peak parasitemia than controls. Mice infected with the lethal variant of P. yoelii were more susceptible to infection when injected with 2dCF after infection, suggesting that 2dCF injection did not directly affect the parasite. Rather, suppression of parasitemia in 2dCF-treated mice may have been mediated by augmented humoral immunity, since 2dCF injection increases antibody responses when 2dCF injection follows antigen (in this case, parasite) injection. Conversely, in mice given 2dCF prior to infection, parasitemia peaked 2 days later and was eliminated more gradually than in control mice. Exposure to 2dCF did not deplete reticulocytes and thus temporarily limit parasitemia. Similarly, enrichment of NK cells or augmentation of macrophage phagocytic activity prior to infection were not sufficient to alter the pattern of infection. In contrast, the pattern of infection in mice treated with tilorone (a macrophage activator which also causes suppressed T-cell function) prior to infection was similar to that observed in 2dCF-exposed animals. These results indicate that 2dCF, given before or after infection, alters the host response to infection with Py17XNL. It appears that a combination of increased macrophage activity and altered T-cell activity contributed to the delay in peak parasitemia and clearance of infection in mice exposed to 2dCF before infection with Py17XNL.

Immune alterations in rats following subacute exposure to tributyltin oxide

Adult male Fischer 344 rats were dosed by oral gavage with bis(tri-n-butyltin)oxide (TBTO) in peanut oil for 10 consecutive days, at dosages ranging from 1.25 to 15 mg/kg/day. Other groups of rats were dosed daily for 10 days by oral gavage with cyclophosphamide (CY) at dosages ranging from 0.75 to 6 mg/kg/day. These rats served as positive controls for the immune assays employed. The immune function parameters examined included the following: delayed-type hypersensitivity (DTH) and antibody responses to bovine serum albumin (BSA), primary antibody responses to sheep red blood cells (SRBC) and trinitrophenyl lipopolysaccharide (TNP-LPS) and enumeration of splenic lymphocyte populations. The DTH and antibody responses to BSA were not affected by TBTO exposure; however these responses were suppressed in rats dosed with CY at 6 mg/kg/day. The plaque forming cell (PFC) response to the T cell-dependent antigen SRBC was enhanced in rats dosed with TBTO at from 5 to 15 mg/kg/day. On the other hand, the PFC response to the T cell-independent antigen TNP-LPS was unaffected by TBTO exposure. Rats dosed with CY had suppressed PFC responses to SRBC and TNP-LPS at dosages of 3 and 6 mg/kg/day, respectively. Enumeration of splenic lymphocyte populations from TBTO-exposed rats revealed a reduction in OX8- but not W3/25- or IgG-positive cells. These results, as well as results from an earlier study from this lab, suggest that T lymphocytes are a primary target for TBTO-induced immune alterations and that the enhancement of the PFC response to SRBC in TBTO-exposed rats may be mediated by alterations in the suppressor (OX8-positive) T lymphocyte population.

Immunotoxicity of tributyltin oxide in rats exposed as adults or pre-weanlings

A comparison was made between adult and pre-weanling rats of the immunotoxic effects of subacute dosing with bis(tri-n-butyltin) oxide (TBTO). Adult (9 weeks old) male Fischer rats were dosed by oral gavage with TBTO for 10 consecutive days at 1.25-10 mg/kg per dose or 3 times/week for a total of 10 doses at 5-20 mg/kg per dose. Adult rats similarly dosed by oral gavage with 6 mg/kg per dose cyclophosphamide (CY) served as positive controls. Pre-weanling rats (3-24 days old) were dosed 3 times/week for a total of 10 doses at 2.5, 5 or 10 mg/kg per dose. At various times after dosing rats were evaluated for alterations in body and lymphoid organ weights, mitogen and mixed lymphocyte reaction (MLR) lymphoproliferative (LP) responses, natural killer (NK) cell activity, cytotoxic T lymphocyte (CTL) responses and primary antibody plaque-forming cell (PFC) responses. In adult rats given 10 daily doses of TBTO, thymic involution was observed at a dosage of 2.5 mg/kg and mitogen responses to Con A and PHA were suppressed at 5 mg/kg. The PFC response was enhanced in adult rats dosed daily at 2.5 mg/kg. A dosage of 5 mg/kg given intermittently (3 times/week) to adults or pre-weanlings resulted in thymic involution. Reductions in mitogen responses were observed in adults dosed intermittently at 10 and 20 mg/kg and in pre-weanlings at 5 and 10 mg/kg. The MLR response was suppressed in adult rats dosed intermittently at 20 mg/kg and in pre-weanling rats at 10 mg/kg. NK cell activity was suppressed only in pups dosed intermittently at 10 mg/kg. CTL responses were not affected in either age group. Within 3 weeks following the last exposure of adult rats to TBTO all parameters returned to normal. On the other hand, LP responses to mitogens were suppressed in 10-week-old rats that were dosed with 10 mg/kg TBTO as pre-weanlings. However, this exposure regimen in reductions in body weight that persisted for up to 13 weeks of age, which suggests that TBTO may be a developmental toxicant. These data indicate that while exposure of young rats to TBTO resulted in immune alterations at doses lower than those required to suppress responses in adults, the observed effects may also be influenced by the developmental toxicity of this compound.

Suppression of lymphocyte proliferation by hexamethylene diamine

The antiproliferative potential of hexamethylene diamine (HMDA) for mitogen-stimulated splenic lymphocytes was evaluated in vitro at final concentrations of 0.1-16 mM. Addition at the start of culture or after 24 or 48 h of culture decreased the proliferative response to T and B cell mitogens. However, the concentration of HMDA required to cause suppression increased with incubation time. Removal of diamine after 24 h allowed cells to proliferate normally upon reculture with mitogen. Mitogenic responses of cultures containing the potent ornithine decarboxylase (ODC) inhibitor alpha-difluoromethylornithine (DFMO) were also inhibited in a time and dose dependent fashion. ODC activity, which was much greater in cultures stimulated with Con A than LPS, was markedly decreased by inclusion of diamine or DFMO in the culture medium. Addition of putrescine to cultures did not reverse the suppressive effects of diamine on proliferation but did restore DFMO-containing cultures to control levels of activity. These results indicate that HMDA does suppress lymphocyte proliferation in vitro by alteration of ODC and polyamine activity. However, comparison of results obtained with DFMO and HMDA suggests that HMDA may act via multiple pathways, only one of which involves inhibition of ODC activity.

Evaluation of the immunotoxicity of low level PCB exposure in the rat

Weanling male Fischer 344 rats were exposed daily by gastric intubation for up to 15 weeks to the polychlorinated biphenyl (PCB) Aroclor 1254 at 0.1, 1, 10, or 25 mg/kg body weight. At 5, 10 and 15 weeks groups of rats were killed and immune functions were evaluated. The immune parameters examined included the following: body and lymphoid organ weights, mitogen-stimulated lymphoproliferative (LP) responses, natural killer (NK) cell activity, mixed lymphocyte reaction (MLR), and cytotoxic T lymphocyte (CTL) response. After 15 weeks of dosing body weights were reduced in rats receiving 25 mg/kg PCB while thymus weights were decreased in rats receiving 10 and 25 mg/kg. NK cell activity was reduced in rats dosed for 15 weeks at 10 and 25 mg/kg. The LP response to phytohemagglutinin was enhanced in rats dosed for 15 weeks at 25 mg/kg PCB. Exposure of rats to PCB did not affect the MLR or CTL responses. Other groups of rats were exposed to cyclophosphamide (CY) and served as positive controls for the immune assays employed. CY induced alterations in all of the immune parameters measured, indicating that this is an appropriate battery of immune function tests which is capable of detecting immune alterations in the rat. Alterations in immune function induced by daily gastric intubation with PCB were accompanied by reductions in body weight and/or hepatomegaly. These results suggest that the observed immune alterations may be related to the overt toxicity of this PCB in the rat.

Immunologic effects of perinatal exposure of rats to dioctyltin dichloride

Studies were conducted to determine the period of immune system development that was most sensitive to perturbation by the known immunotoxicant di-n-octyltin dichloride (DOTC). Fischer 344 rats were exposed prenatally, both pre- and postnatally, or postnatally to DOTC by oral gavage of pregnant and/or lactating females. At various ages, ranging from 3 to 16 wk of age, offspring were examined for a number of immune functions. These included body and lymphoid organ weights; lymphoproliferative responses to B- and T-cell mitogens; natural killer cell activity; and primary antibody response to sheep erythrocytes. Prenatal (10-20 of gestation), pre- and postnatal (d 11-20 of gestation and 2-11 d of age), or postnatal (2-13 d of age) oral dosing of dams with 20-50 mg/kg DOTC resulted in no consistent alteration in immune function in offspring. However, direct oral dosing of rat pups to 5-15 mg/kg DOTC, beginning at 3 d of age and then 3 times per week up to 24 d of age for a total of 10 doses, resulted in significant suppression of the lymphoproliferative response of splenocytes to a T-cell mitogen in 10-wk-old rats (i.e., 7 wk after the last exposure to DOTC). Lymphoproliferative responses returned to control levels by 12 wk of age. In comparison young adult (8 wk old) rats dosed with 10 or 20 mg/kg DOTC under an identical dosing schedule (i.e., 3 times per week for a total of 10 doses) showed no suppression in the mitogen response of splenocytes 4 wk after the last exposure to DOTC. These results suggest that direct dosing of pups during early postnatal life may be the most effective means of inducing immunosuppression with DOTC during immune system development. The results also provide evidence for the greater sensitivity of the developing immune system compared with the fully developed immune system for a known immunotoxicant.

Enhancement of natural killer cell activity and interferon production by manganese in young mice

The effect that MnCl2 has on murine splenic natural killer (NK) cell activity was investigated in infant (10 days old), pre-weanling (18 days old) and weanling (24 days old) C57BL/6J mice. A single intraperitoneal injection of 10, 20 or 40 micrograms MnCl2/g body weight caused a significant enhancement in NK activity, as determined by the in vitro 51Cr release assay. Comparable enhancement of NK activity was observed for age-matched mice injected intraperitoneally with polyinosinic polycytidylic acid (Poly I:C). Both MnCl2 and Poly I:C caused elevations in serum interferon levels. Time-course studies revealed that interferon levels returned to normal within 48 hours following injection with either MnCl2 or Poly I:C; however enhanced NK activity persisted for up to 48 hours in Poly I:C-injected mice and 72 hours in MnCl2-injected mice. The administration of rabbit anti-asialo GMl to MnCl2-injected mice completely abrogated the enhanced NK activity. In addition, the injection of rabbit anti-mouse interferon alpha, beta but not gamma completely abrogated the enhanced NK activity. In addition, the injection of rabbit anti-mouse interferon alpha, beta but not gamma completely abrogated the enhancement of NK activity by MnCl2 and to a lesser extent the enhancement of NK activity by Poly I:C. These results indicate that despite low levels of NK activity in pre-weanling mice, MnCl2 is capable of enhancing this activity by 8-9 fold. Furthermore, Mn-enhanced NK activity in these young mice appears to be mediated by the production of interferon alpha, beta.

The effects of nickel on immune function in the rat

The immunotoxic potential of NiCl2 was evaluated in Fischer 344 rats following a single intramuscular injection at doses ranging from 10 to 20 mg/kg. Twenty-four hours following treatment, selected cellular and humoral immune function parameters were examined. Significant (P less than 0.05) decreases in body weights were observed in rats injected with 15 and 20 mg/kg NiCl2 as were decreases in spleen weights of rats receiving 20 mg/kg. The lymphoproliferative responses of splenocytes to the T cell mitogens concanavalin A (Con A), phytohemagglutinin (PHA), the T and B cell mitogen pokeweed mitogen (PWM) and the B cell mitogen Salmonella typhimurium mitogen (STM) were not significantly different from controls. No significant differences were observed between control and Ni-treated rats in the primary antibody response to sheep red blood cells (SRBC). On the other hand, natural killer (NK) cell activity was significantly (P less than 0.05) suppressed in rats injected with 10, 15, or 20 mg/kg NiCl2. NK cell suppression was observed in both male and female rats and for both allogeneic W/Fu-G1 target cells as well as xenogeneic YAC-1 target cells. Ni-induced suppression of NK activity was transient, with levels returning to control values within three days following treatment. Ni-induced suppression of NK activity was also manifested by an increase in mortality of rats injected with MADB106 tumor cells. These results extend to a second species our earlier findings that Ni suppresses NK activity.

Selective immunotoxic effects in mice treated with the adenosine deaminase inhibitor 2'-deoxycoformycin

Mice were administered the adenosine deaminase inhibitor 2'-deoxycoformycin by daily intraperitoneal injection for five days and evaluated 24 h, 72 h and 6 days after the final dose. Spleen weight was decreased in treated mice for up to 6 days after treatment whereas body weight was significantly affected only at 24 h in mice administered 4 micrograms 2'-deoxycoformycin/g of body weight. The number and relative percentage of circulating lymphocytes were decreased 24 and 72 h after the last injection. Lymphoproliferative responses to T cell mitogens were suppressed for at least 72 h post-treatment whereas the mixed lymphocyte response was normal at 24 h but was depressed at 72 h post-treatment. Conversely, natural killer cell activity was greater in treated mice than in controls for the entire observation period. Data from cell surface marker analysis provided indirect evidence that natural killer effector cells lack sensitivity to 2'-deoxycoformycin. The antibody responses of mice treated with 2 or 4 micrograms 2'-deoxycoformycin/g over four days prior to or after immunization with sheep erythrocytes were suppressed or enhanced, respectively, compared to controls. These results indicate selective effects of 2'-deoxycoformycin on immune function and suggest that subpopulations of lymphocytes differ in the degree of sensitivity to 2'-deoxycoformycin.

Alteration of immune function in mice following carcinogen exposure

Treatment of mice with the direct-acting alkylating agent methyl methanesulfonate produced marked suppression of the humoral response to sheep erythrocytes and suppression of T cell responses to foreign antigens. These effects occurred without loss of spleen, thymus or body weight and in the absence of peripheral blood, splenic or bone marrow cytotoxicity. In comparison, exposure to urethan decreased spleen weights, number and viability of spleen cells, and numbers of circulating lymphocytes. Significant suppression of T cell mitogen responsiveness was observed at all dose levels of urethan. Thymus weights, proliferative responses to the B cell mitogen lipopolysaccharide and delayed hypersensitivity responses were decreased at the highest urethan dose. Cyclophosphamide treatment significantly depressed thymic weight, lymphoproliferative responses of T and B cells, antibody production and delayed hypersensitivity responses. These results suggest differential sensitivity in components of the host defense system to weak carcinogens.

Effects of manganese, calcium, magnesium, and zinc on nickel-induced suppression of murine natural killer cell activity

The effects that divalent metals have on nickel-induced suppression of natural killer (NK) cell activity were studied in mice. Male CBA/J mice were given a single intramuscular injection of metal salt on a body weight basis. The metal doses used were the following: nickel chloride, 4.5-36 micrograms/g; manganese chloride, 20-80 micrograms/g. Twenty-four hours after metal injection, splenic NK cell activity was assessed using a 51Cr-release assay. Ni significantly (p less than 0.01) suppressed NK activity, while Mn significantly (p less than 0.01) enhanced NK activity. No alteration in NK activity was observed in mice injected with Mg, Ca, or Zn. Since these divalent metals have been shown to have antagonistic effects on Ni-induced carcinogenicity and toxicity, they were used in combination with Ni to determine if such antagonisms exist for NK cell activity. The injection of Ni and Mn in combination at a single site resulted in the enhancement of NK activity, although this enhancement was at a level below that observed following the injection of Mn alone. Injection of Mg, Zn, or Ca in combination with Ni did not affect NK activity compared to saline controls. In contrast, the injection of Ni in one thigh followed immediately by Mn, Mg, Ca, or Zn into the other thigh resulted in significant suppression of NK activity for all metals compared with saline controls. An interesting finding was that the injection of Ni followed immediately by Mn into the opposite thigh resulted in even greater reductions in NK activity than Ni alone. Suppression of NK activity by Ni and Mn injected at separate sites was not seen when Mn injection preceded Ni injection by 1 h. These data indicate that both the divalent metal and the timing of its injection relative to Ni injection are critical for altering Ni-induced suppression of NK cell activity.

Immune function in mice exposed to the adenosine deaminase inhibitor 2'-deoxycoformycin during immune system development

Pregnant mice were administered 2'-deoxycoformycin (2dCF), a potent inhibitor of adenosine deaminase activity, by intraperitoneal injection on day 7 or 15 of gestation or from day 8-12 or 14-18 of gestation. A total dose of 0.5 or 2.0 micrograms 2dCF/g of maternal body weight was given to the dams. In a separate study, pups born to nontreated dams were given 5 intraperitoneal injections totaling 0.5, 2.0 or 4.0 micrograms 2dCF/g beginning at 4 weeks of age. Administered doses of 2dCF were at levels known to profoundly suppress adenosine deaminase levels in adult mice. Pups born to dams injected with 2dCF from day 14-18 all died within 48 h of birth whereas other injection schedules had no effect on birth rate or survival of pups. In utero 2dCF exposure had little effect on immune function in offspring. On the other hand, body, spleen and thymus weight, and splenic cellularity were decreased in weanling mice 24 h after the last injection of 4 micrograms/g 2dCF. Proliferative responses of splenocytes to T cell mitogens and alloantigens were likewise suppressed at both 2.0 and 4.0 micrograms/g 2dCF. Suppression of proliferative responses in treated weanling mice were no longer apparent at 7 weeks of age although splenic cellularity and weight remained lower than control values. These results are similar to those we have reported for 8 week old mice given similar doses of 2dCF, with the exception of elevated levels of NK cell activity in older 2dCF-treated mice and suggest that there may be age-related differences in the sensitivity of certain cell populations to the effects of 2dCF.

In vitro augmentation of natural killer cell activity by manganese chloride

The in vitro cultivation of murine spleen cells with MnCl2 resulted in the enhancement of natural killer (NK) cell activity as measured in a 4-h 51Cr-release assay. Optimal enhancement of NK activity was observed at concentrations of 10-20 micrograms MnCl2/culture (72-144 microM Mn2+). Enhancement of NK activity by MnCl2 was not associated with any changes in the number or viability of cells following culture. The addition of antiasialo GM1 antibody and complement to spleen cell cultures completely abrogated the enhancement of NK activity by MnCl2. The enhancement of NK activity by MnCl2 in vitro was accompanied by interferon induction. The addition of rabbit antimouse interferon to spleen cells cultured with MnCl2 reduced NK activity. NK activity in cultures treated with MnCl2 was also reduced upon removal of plastic adherent cells. However, restoration of enhanced NK activity by addition of adherent cells to nonadherent cells in the presence of MnCl2 was not observed. Similar effects of NK activity were observed with polyinosinic-polycytidylic acid (Poly I X C), a known interferon inducer and NK enhancer. The results demonstrate that murine splenic NK activity is enhanced in vitro by MnCl2 and that this enhancement may be mediated by interferon induction. The results also suggest that in vitro enhancement of NK activity by MnCl2, as with Poly I X C, may require participation of an adherent cell population for NK augmentation.

Immunological studies in mice following in utero exposure to NiCl2

The effect that NiCl2 has on the development of immune function in mice was examined in the offspring of dams implanted with mini-osmotic pumps during pregnancy. Time bred C57BL/6J mice were implanted subcutaneously on day 5 of gestation with mini pumps which delivered a total dose of from 9.1 to 73.2 micrograms/g NiCl2. The pumps delivered NiCl2 to the dams through day 19 of gestation. At 8 -- 10 weeks of age the offspring of NiCl2-dosed dams were evaluated for immune function. No consistent significant alterations were observed between control and treated offspring for the following: lymphoid organ or body weights; the lymphoproliferative response to B or T lymphocyte mitogens; the lymphoproliferative response to allogeneic spleen cells in the mixed lymphocyte reaction; the development of syngeneic tumors; or the primary antibody response to sheep red blood cells. Natural killer (NK) cell activity was reduced in offspring exposed to NiCl2 in utero; however, the biological relevance of these reductions is questionable because of the failure to demonstrate an increased susceptibility to the B16-F10 syngeneic tumor. The results indicate that under the conditions and doses employed it appears that NiCl2. does not adversely affect the developing immune system of the mouse.

Immune function of young adult mice following in utero exposure to cyclophosphamide

Long-lasting organic damage has been reported following in utero exposure to certain environmental or therapeutic agents. The sensitivity of the developing immune system to chemical insult during organogenesis or histogenesis was evaluated in mice employing the known immunosuppressive agent cyclophosphamide (CY). Experiments were conducted employing one of the following treatment regimens: (1) 1 microgram/g X d intravenously on d 9-12 or 14-17 of gestation; (2) 5 micrograms/g intravenously on 12 of gestation; (3) 1, 2.5, or 5 micrograms/g X d intraperitoneally on d 12 of gestation; or (4) 5, 10, or 20 micrograms/g intraperitoneally on d 17 of gestation. There were no surviving pups born to mothers administered CY by schedule 2; otherwise, numbers of surviving offspring were not affected by drug treatment, and no gross terata were observed. Employing this variety of exposure protocols, consistent enhancement or suppression of cell-mediated or humoral immune function was not observed in offspring of treated dams. Reduced body weight in 5- and 8-wk-old progeny was noted after exposure to 20 micrograms/g on gestational d 17. Increased in vitro B-lymphocyte blastogenic response to lipopolysaccharide occurred in 5-wk-old animals, and production of antibody to sheep erythrocytes was increased in 8-wk-old offspring exposed to CY at 20 micrograms/g on d 17 of gestation. The T-lymphocyte parameters were relatively unaffected by in utero exposure to CY, suggesting either that cell-mediated immune function was not affected by treatment or that homeostasis was restored prior to immunologic evaluation of offspring.

Evaluation of immune function in mice exposed to Ordram

The potential effects that the thiocarbamate herbicide Ordram has on the immune system of mice was evaluated following 12 days of acute dosing by oral gavage. Dosages of Ordram ranging from 20 to 320 mg/kg/day had no consistent significant effects on a variety of immune parameters investigated. The immune parameters measured were the following: body and lymphoid organ weights; splenic natural killer (NK) cell activity; lymphoproliferative responses to B and T lymphocyte mitogens and allogeneic spleen cells in a one-way mixed lymphocyte reaction; and delayed-type hypersensitivity and antibody responses to sheep red blood cells (SRBC). The effects that the immunosuppressant cyclophosphamide has on these immune parameters was also examined. The results indicate that Ordram does not appear to affect key parameters of the immune system of mice under the conditions of exposure employed.

Manganese chloride enhances natural cell-mediated immune effector cell function: effects on macrophages

A single intramuscular injection of MnC12 in mice caused an increase in macrophage functional activity. Spleen cell antibody-dependent cell-mediated cytotoxicity against both chicken erythrocytes and P815 tumor cell targets was enhanced 24 h following a single injection of MnC12. Enhanced antibody-dependent cell-mediated cytotoxicity activity following MnC12 treatment was not associated with a change in spleen cellularities compared with saline-injected mice. Resident peritoneal macrophages from mice injected intramuscularly with MnC12 displayed enhanced phagocytic activity for chicken erythrocytes in the presence or absence of opsonizing antibody. Enhanced cytolytic activity against P815 mastocytoma target cells and enhanced cytostatic activity against MBL-2 lymphoma target cells was also observed for nonelicited resident peritoneal macrophages from mice injected intramuscularly with MnC12. There were no differences in the cellularity or relative number of adherent cells obtained from the peritoneal cavity of saline or MnC12-injected mice. These enhanced macrophage functions were associated with the induction of increased interferon levels in mice injected with MnC12.

Evaluation of the immunotoxic potential of chlordecone with comparison to cyclophosphamide

The immunotoxic potential of chlordecone was evaluated in male Fischer-344 rats following 10 d of acute dosing by oral gavage. These results were compared with those obtained following a comparable dosing regimen with the known immunosuppressive drug cyclophosphamide. Significant changes in ratios of spleen and thymus to body weight, blastogenic responsiveness of lymphocytes to concanavalin A, and natural killer (NK) cell activity against allogeneic W/Fu-G1 rat lymphoma target cells and xenogeneic YAC-1 mouse lymphoma target cells were observed only at the highest chlordecone dosage (10 mg/kg . d). A significant decrement in body weight also occurred at this dosage which suggests that the observed changes in the immune parameters measured were most likely due to the overt toxicity of chlordecone. In contrast, rats dosed over 10 d by oral gavage with cyclophosphamide showed significant decreases in spleen and thymus to body weight ratios at a dosage as low as 1.5 mg/kg . d. Body weight decrements were observed only at dosages of 12 mg/kg . d or greater. At dosages of 1.5 mg/kg . d or greater, cyclophosphamide caused a significant decrease in the total leukocyte and absolute lymphocyte counts in peripheral blood, and a decrease in the lymphoproliferative responses to both T- and B-lymphocyte mitogens. Significant suppression of NK cell activity was observed at dosages of 6 mg/kg . d or greater. These results suggest that T and B lymphocytes are more sensitive than are NK lymphocytes to the immunosuppressive effects of cyclophosphamide. The results of these two studies indicate that the failure to detect chlordecone-induced immunotoxic effects in the absence of overt toxicity is not due to the possible insensitivity of the parameters examined. Instead, since cyclophosphamide affected all of the parameters tested, these results indicate that the endpoints examined here are capable of detecting immunotoxicity with sufficient sensitivity to permit distinction between probable indirect immunosuppression due to overt toxicity and subtle, direct impairment of the immune system.

Immunologic effects of nickel: I. Suppression of cellular and humoral immunity

The effects of nickel chloride on the cellular and humoral immune responses of mice were studied. A single intramuscular injection of nickel chloride (18.3 mg/kg) caused a significant involution of the thymus within 2 days following treatment. Significant reductions in the in vitro mitogen-stimulated response of lymphocytes from nickel chloride-treated mice (24 hr following a single injection of 18.3 or 36.6 mg/kg) were observed for the T-cell mitogens phytohemagglutinin (PHA) and concanavalin A (Con A), and the B- and T-cell mitogen pokeweed mitogen (PWM) but not the B-cell mitogen lipopolysaccharide (LPS). Theta-positive but not Ig-positive spleen cells were significantly reduced in nickel-treated mice compared with controls. Significant suppression of the primary antibody response to the T-cell dependent antigen sheep red blood cells was observed following a single injection of 18.3 mg/kg NiCl2. Natural killer (NK) cell activity was significantly suppressed following a single injection of 18.3 mg/kg NiCl2. The administration of NiCl2 (18.3 mg/kg) also decreased the amount of endotoxin required to kill 50% of treated mice, although this was not statistically significant. In all cases the immunosuppressive effects of NiCl2 were found to be transient with responses returning to normal within a few days. No alteration in the response of mice immunized with the T-cell independent antigen polyvinylpyrrolidone was observed following treatment with nickel. Furthermore, the phagocytic capacity of resident peritoneal macrophages from nickel-treated mice was not significantly different from saline-injected mice. The results indicate that NiCl2 predominantly affects T-cell mediated immune responses and natural killer cells.

Manganese chloride enhances murine cell-mediated cytotoxicity: effects on natural killer cells

Natural killer (NK) cell activity of mice given a single injection of manganese chloride (MnCl2) was significantly enhanced as measured in a 4-hr in vitro 51Cr release assay. Enhanced activity persisted for several days after injection. This cytotoxic activity was associated with nonadherent spleen cells and was completely eliminated by injecting MnCl2-treated mice with anti-asialo GM1 serum. Manganese-enhanced natural cytotoxicity was observed in several mouse strains with differing NK cell reactivity (CBA/J, C57BL/6, A/J, C3H/HeJ, and C57BL/6 beige mice) and with several tumor target cells with differing sensitivity to NK cytolysis (YAC-1, RBL-5, EL-4, and P815). The growth of B16-F10 melanoma lung tumors was inhibited in mice injected with MnCl2 one day before tumor challenge. Manganese chloride enhancement of NK cell activity appeared to be mediated by interferon (IFN). Low levels of IFN were detected in the serum of mice as early as 4 hr after MnCl2 injection. Rabbit anti-mouse IFN alpha, beta but not anti-mouse IFN gamma completely eliminated the MnCl2-enhanced NK cell activity in the spleens of mice. The observed enhancement of NK cell activity by MnCl2 is similar to that reported for more complex molecules that act by inducing IFN production.

Augmentation of murine natural killer cell activity by manganese chloride

Natural killer (NK) cell activity of spleen cells from male CBA/J mice was augmented by a single parenteral injection of MnCl2 administered 1 day prior to testing by in vitro and in vivo isotope release assays. Increased cytotoxic activity was observed in vitro against both NK-sensitive (YAC-1) and NK-resistant (EL-4) target cells. NK activity was also enhanced in normally low (A/J) and intermediately (C57Bl/6J) reactive strains of mice. Augmentation of NK activity by MnCl2 was accompanied by an increase in circulating interferon (IFN) levels.

Microwaves (2,450 MHz) suppress murine natural killer cell activity

The effect of 2,450-MHz CW microwaves on natural killer (NK) cell activity and lymphocyte responsiveness to mitogen stimulation was studied in mice. Groups of mice were irradiated at power densities of 5, 15, or 30 mW/cm2 (SAR = 3.5, 10.5, and 21 W/kg respectively) for 1.5 h on 2 or 9 consecutive days. NK cell activity was determined using an in vitro 51Cr release cytotoxicity assay and an in vivo tumor-cell clearance assay. No consistent change was observed in the mitogen response of spleen cells from sham compared with irradiated mice. A significant suppression of NK cell activity measured in vitro was observed for mice irradiated at 30 mW/cm2, but not at 15 or 5 mW/cm2. A significant suppression of NK cell activity, as determined using the in vivo tumor clearance assay, was also observed at 30 mW/cm2. NK cell activity, as determined using the in vitro assay, returned to normal within 24 h following the last irradiation. Treatment of mice with hydrocortisone caused suppression of NK cell activity measured in vitro and in vivo. Paradoxically, peritoneal macrophage phagocytosis was enhanced following irradiation at 30 mW/cm2, the power density at which NK activity was suppressed. The possible role that microwave heating plays in producing these effects is discussed.

Assessment of immune function development in mice irradiated in utero with 2450-MHz microwaves

Groups of time-bred pregnant mice were irradiated with 2450-MHz microwaves at an incident power density of 28 mW/cm2 for 100 min daily from day 6 to day 18 of pregnancy. The average specific absorption rate (SAR) was 16.5 W/kg. Two experiments were performed under these conditions. At 3 and 6 weeks of age the mice were assessed for development of the primary immune response to sheep erythrocytes, in vitro mitogen-stimulated lymphocyte proliferation, and natural killer (NK) cell activity. No consistent significant difference in the primary immune response, in the mitogen response, or in the NK cell activity was observed between irradiated and sham-irradiated mice.

Microwave radiation (2450-MHz) potentiates the lethal effect of endotoxin in mice

Groups of male CBA/J mice were injected with Salmonella typhimurium lipopolysaccharide (LPS) and irradiated with 2450 MHz (CW) microwaves. The 50% lethal dose (LD50) of LPS was determined for mice irradiated at 30, 20, 10 and 5 mW/cm2 immediately following injection. The average specific absorption rate was approximately 0.6 W/kg per 1 mW/cm2 incident power. An equal number of animals served as sham-irradiated controls for each power density. The mice were placed individually in small containers and were maintained at 22 degrees C and 50% relative humidity during a 2 hour irradiation period. Following irradiation the mice were returned to their home cages and were observed for 48 hr. A significant decrease in the LPS dose required to kill 50% of the mice was observed at power densities of 20 and 30 mW/cm2. High ambient temperature (37 degrees C) also potentiated the lethal effect of endotoxin. Microwave irradiation prior to LPS injection, however, did not affect the lethal action of LPS.

Assessment of the immune responsiveness of mice irradiated with continuous wave or pulse-modulated 425-MHz radio frequency radiation

Groups of female BALB/C mice were irradiated with 425-MHz radio frequency (RF) radiation either continuous wave (CW) or pulse modulated (PM, 1-ms pulse width, 250 pulses/s). Mice were irradiated in a rectangular strip-transmission line at average forward powers of 78, 17.7, or 5 W for CW and 17.7, 5, or 1.25 W for PM. The mean specific absorption rate, as measured using twin-well calorimetry was 7.7 W/kg for a forward power of 70 W. No differences in the mitogen-stimulated response of lymphocytes or in the primary antibody response to sheep erythrocytes or polyvinylpyrrolidone were observed between irradiated and sham-irradiated mice, nor between mice exposed to either CW or PM 425-MHz RF radiation.

Complement receptor positive spleen cells in microwave (2450-MHz)-irradiated mice

Male CBA/J mice were exposed under far-field conditions in a temperature and humidity controlled environment to 2450-MHz (CW) microwaves. Mice were exposed once for 30 minutes at a power density of 15, 20, 30, or 40 mW/cm2. The whole-body-averaged dose rate was approximately 0.7 mW/g per mW/cm2. Six days after irradiation, the percentage of complement-receptor-positive (CR+) spleen cells was determined. No difference was observed in the percentage of CR+ spleen cells of young adult (10-12-week-old) mice exposed at any of the power densities as compared with sham-irradiated controls. However, a significant (P less than .05) increase was observed in the percentage of CR+ cells from 16-week old mice exposed at 40 mW/cm2. This increase in CR+ cells was accompanied by a significant (P less than .05) decrease in the number of nucleated cells in the spleens of these mice. This change in CR+ and nucleated spleen cells was not consistently produced. The available data indicate that the age and strain of the mouse, the microwave exposure characteristics, and the environmental conditions may all be sources of variation that affect the CR+ end point.