Oral exposure to atrazine modulates cell-mediated immune function and decreases host resistance to the B16F10 tumor model in female B6C3F1 mice.

Atrazine (ATZ) is used throughout North America to control annual broadleaf weeds and grasses in various crops including; corn, sorghum, and sugar cane. Unfortunately, contamination of surface and ground water has occurred as a result of ATZ's chemical and physical properties, and its widespread use throughout the U.S. Midwest. A study of ATZ's immunomodulatory properties was conducted using female B6C3F1 mice and a panel of immune assays and host resistance models designed to evaluate cell-mediated and antibody-mediated immunity. Mice were administered ATZ by gavage (0, 24, 250, and 500 mg/kg/day) for 14 days then evaluated for immune responsiveness. ATZ treatment significantly increased the number of splenic CD8+ T cells, cytotoxic T cell and mixed leukocyte responses, and dose-dependently reduced host resistance to B16F10 melanoma. Thymus and spleen weights, total spleen cell numbers and fixed macrophage function was also reduced in mice that were exposed to ATZ. These results demonstrate that oral ATZ exposure is sufficient to alter cell-mediated immune function and disease resistance in female B6C3F1 mice.

Dietary methoxychlor exposure modulates splenic natural killer cell activity, antibody-forming cell response and phenotypic marker expression in F0 and F1 generations of Sprague Dawley rats.

Methoxychlor, a chlorinated hydrocarbon pesticide, is a persistent environmental contaminant that has been identified in human reproductive tissues. Methoxychlor has been shown to be estrogenic in both in vivo and in vitro studies. As an endocrine disrupter, it may have the potential to adversely affect endocrine, reproductive, and immune systems in animals. The present study evaluated methoxychlor's immunotoxic potential in F0 (dams) and F1 generations of Sprague Dawley rats exposed to an isoflavone-free diet containing methoxychlor at concentrations of 10, 100, and 1000 ppm. In dams, exposure to methoxychlor from gestation day 7 to postpartum day 51 (65 days total exposure) produced a significant increase in the NK activity (1000 ppm) and the percentages of T cells (1000 ppm), helper T cells (1000 ppm) and macrophages (100 and 1000 ppm). In contrast, a decrease in the numbers of splenocytes and B cells was observed at the 100 and 1000 ppm concentrations. In F1 males, exposure to methoxychlor gestationally, lactationally and through feed from postnatal day 22-64 (78 days total exposure) produced an increase in the spleen IgM antibody-forming cell response to sheep red blood cells (100 and 1000 ppm) and the activity of NK cells (1000 ppm). However, there was a decrease in the terminal body weight (1000 ppm), spleen weight (1000 ppm), thymus weight (100 and 1000 ppm), and the numbers of splenocytes (1000 ppm), B cells (100 and 1000 ppm), cytotoxic T cells (1000 ppm) and NK cells (100 and 1000 ppm). In F1 females, exposure to methoxychlor produced a decrease in the terminal body weight (1000 ppm) and the percentages of cytotoxic T cells (10, 100 and 1000 ppm). These results demonstrate that developmental and adult dietary exposure to methoxychlor modulates immune responses in Sprague Dawley rats. Immunological changes were more pronounced in the F1 generation male rats that were exposed during gestation and postpartum, when compared to the F0 and F1 generation females. Increases in antibody-forming cell response and NK cell activity, and altered spleen cell subpopulation numbers were observed in the F1 generation male rats, without similar changes to the F1 generation females.

Thalidomide modulation of the immune response in female B6C3F1 mice: a host resistance study.

Previously, we have reported that thalidomide (Thd) treatment can modulate the immune responses in female B6C3F1 mice. The present study was designed to evaluate whether or not these immunomodulatory responses were of sufficient magnitude to alter host resistances in a number of pathogen and tumor models. B6C3F1 mice were treated intraperitoneally with Thd (30-150 mg/kg) for 14 or 28 days, then inoculated with either Plasmodium yeolii, PYB6 fibrosarcoma tumor cells, B16F10 melanoma tumor cells, Listeria monocytogenes, or Streptococcus pneumoniae. Significant dose-dependent protection against B16F10 and L. monocytogenes was observed in mice that were treated with Thd. Furthermore, time course study using bacterial colony-forming units per spleen and liver as the endpoints indicated that the protective effect of Thd on host resistance to L. monocytogenes was time-dependent. In contrast, Thd treatment did not affect host resistance to P. yeolii, S. pneumoniae and PYB6 tumor. Additionally, the effect of Thd on the phagocytic function of the mononuclear phagocyte system (MPS) was evaluated following intravenous injection of 51Cr-labeled sRBCs. The overall phagocytic activity of MPS was not significantly altered by Thd treatment. In conclusion, these results demonstrate that Thd immunomodulation altered host resistance to B16F10 and L. monocytogenes; and selective modulation of Thd on the immune system may be responsible for the pathogen or tumor-specific effect of this compound.

Sodium metasilicate hypersensitivity in BALB/c mice.

BACKGROUND: Sodium metasilicate (SMS) is a key ingredient for a number of industrial and consumer products. Although little is known about potential for this chemical to cause allergic reactions, a similar silicate compound, sodium silicate, was reported to elicit IgE-mediated contact urticaria. OBJECTIVE: The aim of this study was to evaluate the potential for sodium metasilicate to elicit an allergic response in female BALB/c mice after dermal exposure. METHODS: The primary irritancy assay (IA), local lymph node assay (LLNA), and a mouse ear swelling test (MEST) were used to evaluate the hypersensitivity response elicited by SMS exposure. An evaluation of lymph node subpopulations, cytokine mRNA expression, and serum IgE levels was also conducted. RESULTS: SMS caused significant dermal irritation at concentrations >or=6% and an allergic response after mice were sensitized with 4% SMS then challenged with 6% SMS in the MEST. Lymph node cell proliferation was not observed in the LLNA after treatment with SMS (2% to 6% SMS). Increases in lymph node cellularity, the percentage of B cells, and the expression of certain cytokine mRNAs were observed in mice treated with SMS. Changes in the concentration of serum IgE after SMS treatment, however, were not observed. CONCLUSIONS: SMS appears to elicit a chemical hypersensitivity response in mice, as indicated by the MEST, but not by the LLNA. Increases in auricular lymph node cellularity, the percentage of B cells, and certain cytokine mRNAs support classifying SMS as a weak chemical allergen.

Genistein modulates splenic natural killer cell activity, antibody-forming cell response, and phenotypic marker expression in F(0) and F(1) generations of Sprague-Dawley rats.

The potential effects of the phytoestrogen genistein (GEN) on the immune system were evaluated in both F(0) (dams) and F(1) generations of Sprague-Dawley rats exposed to a soy-free diet containing low (L: 25 ppm), middle (M: 250 ppm), and high (H: 1250 ppm) levels of GEN. In dams, exposure to GEN from Gestation Day 7 to Postpartum Day 51 (totally 65 days) produced a significant increase in NK cell activity (M and H), while a decrease in the percentage of helper T cells (H). In F(1) males, exposure to GEN gestationally, lactationally, and through feed from Postnatal Days 22 to 64 (total 78 days) produced an increase in the relative weights (% body) of spleen (L and H) and thymus (L). Furthermore, exposure to GEN increased the number of splenic B cells (H), T cells (L, M, and H), and T-cell subsets (L, M, and H). Although GEN decreased the percentages of splenic NK cells (L, M, and H), no effect on the activity of NK cells was observed. In F(1) females, exposure to GEN produced a decrease in terminal body weight (H), with an increase in the relative weight of spleen (L, M, and H). Exposure to GEN also increased the number of splenic B cells (L), macrophages (L and M), T cells (H), helper T cells (L and H), and cytotoxic T cells (M and H). Additionally, exposure to GEN increased the percentages of T cells (M and H), helper T cells (H), and cytotoxic T cells (M and H). Moreover, the spleen IgM antibody-forming cell response to sheep red blood cells was enhanced (H), although the percentages of B cells were decreased (M and H). No effect on the activity of NK cells was observed; however, the percentages of splenic NK cells were decreased by GEN (L and H). In conclusion, these results demonstrate that exposure to GEN can modulate the immune responses in Sprague-Dawley rats. Furthermore, the sexual dimorphic effects of GEN in F(1) male and female rats suggest that there may be interactions between GEN and the responses modulated by sex hormones.

Genistein and methoxychlor modulate the activity of natural killer cells and the expression of phenotypic markers by thymocytes and splenocytes in F0 and F1 generations of Sprague-Dawley rats.

The isoflavone genistein (GE) and methoxychlor (MXC) have been shown to be estrogenic in both in vitro and in vivo experimental systems. The objective of the present study was to evaluate the effects of GE and MXC on the immune system in adult and developing rats and the potential interaction between these compounds in their immunomodulatory actions. Timely pregnant Sprague-Dawley rats were exposed to GE (300 or 800 ppm), MXC (800 ppm), or their combinations in feed starting on day 1 of gestation. The offspring were exposed to these chemicals gestationally and lactationally. Immunological evaluation was performed on postnatal day 22. In F0 females, exposure to GE had no effect on the percentages of thymocyte subsets, but caused a significant decrease in the absolute thymus weight at the 800-ppm dose level. In the spleen, GE did not affect the activity of natural killer cells but induced changes in the percentages of splenic T lymphocyte subsets. Exposure to MXC produced no effect on the immune parameters examined except for a decrease in the percentage of CD4+CD8- thymocytes. Additionally, minimal interaction between GE and MXC was observed. In F(1) males, both GE and MXC decreased the percentage of CD4+CD8- thymocytes, but only GE increased spleen natural killer cell activity. MXC in combination with 300 ppm-GE, but not separately, produced significant decreases in the absolute weights of thymus and spleen. In F1 females, GE decreased the percentage of CD4+CD8- thymocytes, increased the percentage of CD4+CD8+ thymocytes, and decreased the activity of spleen natural killer cells. In contrast, MXC increased the percentages of spleen natural killer cells and CD8+ T cells. Overall, the results demonstrate that both GE and MXC can modulate the immune system with greater effects observed in developing rats. Moreover, male and female rats have differential responses to these compounds. A lack of interaction between these two estrogenic chemicals in modulating these immune parameters indicates that their effects on the immune system might involve other mechanisms in addition to the estrogen receptors.

Genistein modulates immune responses and increases host resistance to B16F10 tumor in adult female B6C3F1 mice.

The isoflavone genistein (4,7,4'-trihydroxyisoflavone) is a phytoestrogen found in high levels in soy products that has been associated with decreased incidences of breast and prostate cancers. The potential effects of genistein on the immune system were evaluated in adult female B6C3F1 mice. Groups of mice were exposed to vehicle or genistein by gavage for 28 d. The doses of genistein used were 2, 6 and 20 mg/kg body. Consistent with the chemopreventive effect of genistein, exposure to this compound significantly increased host resistance to B16F10 tumor as reflected by a decrease in the number of lung tumor nodules after tumor cell injection at the middle and high dose levels. Inhibition of B16F10 tumor formation was not due to a direct effect of serum genistein and/or its metabolites on the proliferation of B16F10 tumor cells. When innate and acquired immune responses were evaluated, a dose-related increase of cytotoxic T-cell activity was observed in genistein-treated mice with significant changes observed at the middle and high dose levels. Furthermore, in vitro interleukin (IL)-2-stimulated natural killer (NK) cell activity was significantly enhanced in the high genistein dose group, although the basal NK cell activity was not affected. Although no affect on the mixed lymphocyte responses and anti-CD3 antibody-mediated splenocyte proliferation was observed, exposure to genistein significantly increased basal splenocyte proliferation. Exposure to genistein did not alter the activity of the mononuclear phagocyte system and the cytotoxic/cytostatic function of thioglycollate-recruited peritoneal cells on B16F10 tumor cells. Finally, exposure to genistein did not produce biologically meaningful changes in spleen immunoglobulin (Ig)M and IgG antibody-forming cell responses. In conclusion, genistein enhanced host resistance as evaluated in the B16F10 tumor model, which may be related to the increases in the activities of cytotoxic T cells and NK cells.

Correlation of suppressed natural killer cell activity with altered host resistance models in B6C3F1 mice.

A number of methods have been developed to assess the impact of a xenobiotic on the various components of the immune system. For risk analysis, it is necessary to determine what degree of chemically induced immune perturbation translates into altered host resistance. Natural killer (NK) cells play a pivotal role in the innate immune system with the ability to lyse cells infected with intracellular pathogens and certain tumors without previous exposure to the antigen. Spontaneous NK activity in B6C3F1 mice could be incrementally and consistently decreased by 20 to > or =80% by the intravenous administration of a range of dilutions of anti-asialo GM1 (AAGM1) antibody. The decrease in spontaneous NK activity following a single iv administration of AAGM1 antibody persisted for up to approximately 3 weeks when the initial suppression (e.g., 24 h after AAGM1 antibody injection) was almost 100%. Treatment with AAGM1, however, did not appear to perturb the function of other immune cells, based on results of the plaque assay, the mixed lymphocyte response, the cytotoxic T lymphocyte assay, the reticuloendothelial system clearance of sRBC assay, and the Streptococcus pneumoniae host resistance assay. Following a > or =80% decrease in spontaneous NK activity in mice, challenge with > or =1 x 10(3) B16F10 melanoma cells resulted in an increase in tumor burden based on the number of lung nodules. However, following challenge with 1 x 10(5) melanoma cells, a significant increase in tumor burden in mice was not observed until spontaneous NK activity had been decreased by > or =50-60%. Altered host resistance is a function not only of the magnitude of the decrease in NK activity but also of the magnitude of the challenge to the host.

Evaluation of the immunomodulatory effects of the disinfection by-product, sodium chlorite, in female B6C3F1 mice: a drinking water study.

Sodium chlorite is an inorganic by-product of chlorine dioxide formed during the chlorination of drinking water. Relatively little is known about the adverse health effects of exposure to sodium chlorite in drinking water. In this study, we evaluated sodium chlorite's immunomodulatory properties using female B6C3F1 mice and a panel of immune assays that were designed to evaluate potential changes in innate and acquired cellular and humoral immune responses. Female B6C3F1 mice were exposed to sodium chlorite in their drinking water (0, 0.1, 1, 5, 15, and 30 mg/L) for 28 days, and then evaluated for immunomodulation. Overall, minimal toxicological and immunological changes were observed after exposure to sodium chlorite. Increases in the percentages of blood reticulocytes, and the relative spleen weights were both observed at different sodium chlorite treatment levels; however, these increases were not dose-dependent. An increasing trend in the number of spleen antibody-forming cells was observed over the range of sodium chlorite concentrations. This increase was not, however, significant at any individual treatment level, and was not reflected by changes in serum IgM levels. A significant increase (26%) in the total number of splenic CD8+ cells was observed in mice treated with 30 mg/L of sodium chlorite, but not at the other concentrations. Splenic mixed leukocyte response and peritoneal macrophage activity were unaffected by sodium chlorite. Lastly, exposure to sodium chlorite did not affect natural killer cell activity, although a decrease in augmented natural killer cell activity (42%) was observed at the lowest sodium chlorite treatment level. These results suggest that sodium chlorite, within the range 0.1-30 mg/L, produces minimal immunotoxicity in mice.

Immunotoxicity of sodium bromate in female B6C3F1 mice: a 28-day drinking water study.

Bromate is one of the water disinfection by-products (DBPs) produced during the process of ozonation. The purpose of this study was to evaluate the immunotoxic potential of sodium bromate (SB) in female B6C3F1 mice. SB was administered in the drinking water for 28 days at doses of 80-800 mg/l. There was no difference in drinking water consumption between the animals exposed to SB and the tap water controls. Exposure to SB did not produce any signs of overt toxicity. Furthermore, no significant differences were observed in body weight, body weight gain, or the weights of thymus, liver, kidneys or lungs. No gross pathological lesions were observed in SB-treated animals. However, animals exposed to SB had a significant increase in absolute (28%) and relative (26%) spleen weights. The erythrocyte count, hemoglobin, hematocrit, mean corpuscular volume (MCV), platelet count, total leukocyte count, and counts of differential leukocytes were unaffected by SB. A dose-related increase in reticulocytes was observed following exposure to SB with the greatest increase (78%) observed at the highest dose level. Overall, there were no changes in the absolute number of total T cells, CD4+CD8- T cells, CD4-CD8+ T cells, natural killer (NK) cells and macrophages. Exposure to SB did not affect the percentage of B cells, although a slight increase in absolute number of B cells at the dose of 600 mg/l was observed. There was no alteration in IgM antibody-forming cell (AFC) response, mixed leukocyte reaction (MLR) and NK cell activity after exposure to SB. When the activity of peritoneal macrophages, unstimulated or stimulated with IFN-gamma and LPS, was evaluated using the cytotoxic/cytostatic assay of B16F10 tumor cells, the suppressive effect of macrophages on the proliferation of B16F10 tumor cells was decreased after exposure to SB. In conclusion, SB, when administered in the drinking water at doses from 80 mg/l to 800 mg/l, produced minimal toxicological and immunotoxic effects in female B6C3F1 mice.

Evaluation of the immunomodulatory effects of the macrolide antibiotic, clarithromycin, in female B6C3F1 mice: a 28-day oral gavage study.

The macrolide antibiotic, clarithromycin, is used extensively to treat bacterial infections associated with pneumonia, duodenal ulcers, and the advanced stages of human immunodeficiency viral (HIV) infection. In addition to its antimicrobial properties, several studies have indicated that clarithromycin also has anti-inflammatory and immunomodulatory properties. In this study, clarithromycin's immunomodulatory properties were evaluated using female B6C3F1 mice and a panel of immune assays that were designed to evaluate potential changes in innate, and acquired cellular and humoral immune responses. Female B6C3F1 mice were treated daily by gavage with clarithromycin (0, 125, 250, and 500 mg/kg) for 28 days then evaluated for immunomodulation. Minimal immunological changes were observed after 28 days of treatment. A slight increase in the number of spleen antibody-forming cells was observed at the 250 mg/kg treatment level, but not at other doses. Serum IgM levels were unaffected by the clarithromycin treatment. A significant increase in the number of splenic macrophages was also observed in mice treated with 125 mg/kg of clarithromycin, but this increase was not observed at the other treatment levels. Innate and cell-mediated immunity, as measured by natural killer cell activity, and mixed leukocyte and cytotoxic T cell response, respectively, were unchanged following treatment with clarithromycin. These results suggest that the immune system is not a target for clarithromycin at doses of 500 mg/kg or below.

Dermal exposure to cinnamaldehyde alters lymphocyte subpopulations, number of interferon-gamma-producing cells, and expression of B7 costimulatory molecules and cytokine messenger RNAs in auricular lymph nodes of B6C3F1 mice.

BACKGROUND: Although the Murine Local Lymph Node Assay (LLNA) is efficient in identifying chemicals with sensitizing potential, there is increasing need for alternative end points. Cinnamaldehyde (CIN) was chosen for evaluation based on its moderate potency and extensive use in fragrance materials. OBJECTIVES: The purpose of the present studies is to incorporate some alternative end points, such as phenotypic analysis and cytokine production, into a modified LLNA/irritancy assay (IA) to evaluate the sensitization of female B6C3F1 mice to CIN. METHODS: Several nontraditional end points, including the analysis of lymphocyte subpopulations, B7 costimulatory molecule and cytokine messenger RNA (mRNA) expression, and intracellular interferon-gamma (IFN-gamma) levels, were incorporated into a modified murine local lymph node (LLNA)/irritancy assay (IA) to evaluate the sensitization of female B6C3F1 mice to cinnamaldehyde (CIN). RESULTS: The alternate end points used in these studies support the classification of CIN as a moderately potent sensitizer. Dermal treatment with CIN resulted in an increase in the percentage of B cells in the auricular lymph nodes (ALNs) and expression of the costimulatory molecule, B7-2, on B cells. Lymph node cells also showed increased transforming growth factor-beta1, migration-inhibition factor, and mild increases in IFN-gamma and interleukin-2 cytokine mRNA expression. Although the increase in IFN-gamma mRNA expression did not translate into increased intracellular IFN-gamma levels, the absolute number of T cells producing IFN-gamma in the ALNs increased. Conversely, the MEST did not classify CIN as a contact allergen. CONCLUSION: The nontraditional end points used in the LLNA/IA were not as sensitive as the traditional radioisotope method used to assess cell proliferation. However, they may help identify compounds inappropriately classified as sensitizers or nonsensitizers by the LLNA and MEST.

Carbon tetrachloride is immunosuppressive and decreases host resistance to Listeria monocytogenes and Streptococcus pneumoniae in female B6C3F1 mice.

Carbon tetrachloride (CCl(4)) is an environmental contaminant that has been detected in ambient air, seawater, surface-water and snow. The immunotoxic potential of CCl(4) was evaluated in female B6C3F1 mice. The animals were administered with CCl(4) daily for 14 days at doses of 50, 100, 500 or 1000 mg/kg body weight by gavage with corn oil as a vehicle. Exposure to CCl(4) resulted in an increase of liver weight but not the body weight and the weights of brain, spleen, lungs, thymus and kidneys. Exposure to CCl(4) produced minimal effect on differential hematological parameters; however, it produced a significant increase in serum glutamic-pyruvic transaminase (SGPT) levels in all dose groups while other serum chemistries showed sporadic increases, primarily at the dose level of 1000 mg/kg. Exposure to CCl(4) produced a decreased humoral immune response; the IgM antibody forming cell (AFC) response to sheep red blood cells (sRBC) was suppressed with the maximal decrease (45%) observed at the dose level of 1000 mg/kg. The IgM serum titer to sRBC was also reduced with a maximal decrease (54%) observed at the dose level of 500 mg/kg. Although exposure to CCl(4) had no effects on the mixed leukocyte response (MLR), cytotoxic T lymphocyte activity and natural killer (NK) cell activity, a decrease in both the absolute number and the percentage of CD4(+)CD8(-) at the dose level of 500 mg/kg was observed. The functional activity of the mononuclear phagocyte system was compromised as reflected by a decrease in the vascular clearance of (51)Cr-sRBC and a decrease in the uptake of (51)Cr-sRBC by the liver. Finally, in the two host resistance models evaluated, exposure to CCl(4) decreased host resistance to both Streptococcus pneumoniae and Listeria monocytogenes with greater susceptibility to the latter. Overall, these studies demonstrate that CCl(4) was immunosuppressive in female B6C3F1 mice.

TNF-alpha blockade by a dimeric TNF type I receptor molecule selectively inhibits adaptive immune responses.

Tumor necrosis factor-alpha (TNF-alpha) is a mediator of severe inflammatory processes, including rheumatoid arthritis. Suppression of TNF with a soluble type I or type II receptor molecule (TNF-RI or TNF-RII) has the potential to decrease cytokine levels and modulate inflammatory diseases in humans. However, it has recently been reported that treatment of mice with a TNF-RI:Fc immunoadhesin protein augmented Gram positive infections and subsequent mortality. To determine if TNF-alpha blockade with soluble TNF-alpha receptors might alter immune system function, assays were assessed in rodents treated with a dimeric form of the p55 TNF-RI, Tumor Necrosis Factor-binding protein (TNFbp). Administration of TNFbp resulted in suppression of primary and secondary IgG antibody responses and cell-mediated immune function. No treatment-related differences were detected in immune-enhancing assays or non-specific immune function parameters. Bacterial host resistance assays with Listeria monocytogenes, Staphylococcus aureus or Escherichia coli showed an increase in tissue colony counts only with L. monocytogenes challenged animals following TNFbp administration. These results suggest that TNFbp has the capacity to inhibit adaptive immune function in experimental animal models. Studies suggest that while reducing TNF-alpha is important in controlling cytokine-dependent disease states, maintenance of a threshold level may be critical for normal immune function.

Influence of MHC background on the antibody response to detergent enzymes in the mouse intranasal test.

The mouse intranasal test (MINT) was developed to assess the immunogenic potential of detergent enzymes. The BDF1 mouse (H-2(b/d)), a cross of C57Bl/6 (H-2(b)) x DBA/2 (H-2(d)) has been used for most of the development work. Preliminary data in the CB6F1(H-2(d/b)), a cross of Balb/c (H-2(d)) x C57Bl/6 showed that this strain was similar to the BDF1 in its response to enzymes. These data also showed that the parental strains responded differently to the enzymes. To understand better the influence the major histocompatibility complex (MHC) background has on immune responses to enzymes, 3 different enzymes were tested in 4 inbred strains (C57Bl/6, DBA/2, Balb/c, and C57Bl/10), 2 hybrid strains (BDF1 and CB6F1), and 2 congenic strains (Balb.B10 and B10.D2). BDF1 mice rank enzymes the same as the guinea pig, which in turn correlates with sensitization in occupationally exposed humans. The ranking is based upon the dose of enzyme needed to give one-half maximal IgG1 antibody response (ED(50)) where Termamyl is more potent than Alcalase, which is equipotent to Savinase. The H-2(d) strains ranked the enzymes the same as the BDF1 but generated ED(50)s for the proteases that were one order of magnitude greater than the BDF1 ED(50)s. The response to Termamyl was the same in the two F1 strains and the H-2(d) strains. The H-2(b) strains did not rank the enzymes the same as BDF1 but the ED(50)s for the proteases were similar to the ED(50)s in the F1 strains. The response to Termamyl in the H-2(b) strains was lower than the response in the F1 and H-2(d) strains. Initial data show that the inbred strains will make enzyme-specific IgE antibody to high doses of enzyme with DBA/2 > Balb/c > C57Bl/6 in terms of the robustness of the response. The IgG1 responses in the congenic strains were similar to the responses in the H-2 matched strains. In addition, the antibody response to enzymes was consistent regardless of the source of BDF1 mice. The responses to these enzymes are clearly MHC linked with a role for Class II I-E molecules indicated. The current data strongly support the use of the F1 hybrid as an appropriate strain for evaluating allergic responses to enzymes.

Oxymetholone modulates cell-mediated immunity in male B6C3F1 mice.

Oxymetholone is a synthetic androgen, structurally related to testosterone. It is currently used to treat anemias, but has also been abused as a performance enhancing anabolic steroid by the sport community. Concern about its suspected immunomodulatory properties provided the incentive for a detailed investigation into its effects on the mammalian immune system. In this study, male B6C3F1 mice were treated for 14 d with oxymetholone (0, 50, 150, and 300 mg/kg) by gastric intubation, then evaluated for immunotoxicity using a panel of immunotoxicity assays. Except for an increasing trend in kidney and liver weights, and a dose-dependent increase in serum blood urea nitrogen levels, no other signs of systemic toxicity were observed. Bone marrow DNA synthesis was reduced, though this did not translate into alterations in myeloid or monocyte colony forming units. Spleen B and T cell numbers, antibody response to sheep red blood cells, proliferative response to both mitogen and immunoglobulin receptor immunogens, and NK cell activity were all unaltered in mice treated with oxymetholone. Peritoneal macrophage activity was also unaffected by oxymetholone treatment. A 38% decrease in the spleen cell mixed leukocyte response, and a 15% decrease in cytotoxic T cell activity, measured in the highest oxymetholone treatment group, indicate that cell-mediated immunity was impaired following exposure. This immunomodulation did not however, translate into a change in host resistance to Listeria monocytogenes.

Glycidol modulation of the immune responses in female B6C3F1 mice.

The immunotoxic potential of glycidol was evaluated in female B6C3F1 mice using a battery of functional assays and three host resistance models. Glycidol was administered to the animals by oral gavage as a solution in sterile distilled water daily for 14 days at doses of 25, 125 and 250 mg/kg. In tier I, we observed that glycidol exposure produced a dose-related decrease in splenocyte IgM antibody-forming cell response to sheep red blood cells (sRBC); the spleen natural killer (NK) cell activity was also decreased. A decrease in B cell proliferative responses to anti-IgM F(ab')2 and/or interleukin-4 (IL-4) was observed while the splenocyte proliferative responses to T cell mitogen ConA and B cell mitogen LPS were not affected. The splenocyte proliferative response to allogeneic cells as evaluated in the mixed leukocyte reaction (MLR) to DBA/2 spleen cells was not affected. In tier II, we found that exposure to glycidol decreased the number and percentage of B cells and the absolute number of CD4+ T cells in the spleen while the number of total T cells, CD8+ T cells and CD4+CD8+ T cells was not affected. The cytotoxic T lymphocyte (CTL) response to mitomycin C-treated P815 mastocytoma was not affected; the cytotoxic activity of peritoneal macrophages was not suppressed. Moreover, the host resistance to Listeria monocytogenes was not affected although a slight increase in host resistance to Streptococcus pneumoniae was observed. However, exposure to glycidol decreased host resistance to the B16F10 melanoma tumor model with the maximal tumor formation in lung observed in the high dose group. Overall, these dada support the finding that glycidol is an immunosuppressive agent in female B6C3F1 mice.

Thalidomide stimulates splenic IgM antibody response and cytotoxic T lymphocyte activity and alters leukocyte subpopulation numbers in female B6C3F1 mice.

Thalidomide has been shown to have antiinflammatory and, more recently, immunomodulating properties, which are beneficial for the treatment of an ever-increasing list of immune related diseases. Although considerable knowledge regarding thalidomide s antiinflammatory properties has been acquired, relatively little is known about its immunomodulating properties in vivo. In this paper, a panel of immune assays was used to evaluate immunomodulation in female B6C3F1 mice treated intraperitoneally for 28 days with thalidomide (30, 100, or 150 mg/kg/day). Spleen antibody forming cell response was significantly enhanced by 37% in mice treated with 150 mg/kg/day, despite an 8% decrease in the percentage of Ig+ B cells. A significant stimulatory trend was observed for the cytotoxic T cell response across thalidomide treatment groups. An evaluation of the spleen leukocyte subpopulations revealed a 23% increase in the absolute number of CD8+ T cells in the 150 mg/kg treatment group and a 9 and 11% decrease in the absolute number of NK cells in both the 100 and 150 mg/kg thalidomide treatment groups, respectively. These findings demonstrate that, in addition to modulating spleen leukocyte numbers, thalidomide also stimulates murine humoral and cellular immune responses in vivo.

Toxicology and humoral immunity assessment of octamethylcyclotetrasiloxane (D4) following a 28-day whole body vapor inhalation exposure in Fischer 344 rats.

Octamethylcyclotetrasiloxane, D4, is a low viscosity, silicone fluid consisting of four dimethyl-siloxy units ((CH3)2SiO)4 in a cyclic structure. It is primarily used as a building block in the industrial synthesis of long chain silicone polymers. The combination of D4 with decamethylcyclopentasiloxane (D5) is commonly referred to as cyclomethicone which has a wide range of applications as a formulation aid in personal care products. To extend the existing database regarding the biological activities of D4, a 28 day whole body vapor inhalation study was conducted using Fischer 344 rats at 0 (room air), 7, 20, 60, 180 and 540 ppm for 6 hours/day, 5 days/week. Parameters measured included body weights, organ weights, gross pathology, histopathology, serum chemistries, and urinalysis. In addition to these standard toxicological endpoints, the ability of D4 exposed animals to mount an IgM antibody response was evaluated by a splenic antibody forming cell (AFC) assay and a serum enzyme-linked immunosorbant assay (ELISA). The results of this 28-day inhalation study indicate that D4 exposure caused no adverse effects on body weight, food consumption, or urinalysis parameters. In addition, there were no exposure related histopathological alterations at any site for any exposure group. A statistically significant increase in liver weight and the liver to body weight ratio was observed in both male (180-540 ppm) and female (20-540 ppm) rats, which was not observed in the 14-day recovery group animals. There were no other significant organ weight changes. Although statistically significant changes were observed in several hematological and serum chemistry parameters in both the terminal and 14-day recovery animals, the changes were marginal and within the normal range of values for the rat. Under these experimental conditions, there were no alterations noted in immune system function at any of the D4 exposure levels.

Immunological evaluation of the mycotoxin patulin in female B6C3F1 mice.

Patulin is a mycotoxin produced by many fungal species of the genera Penicillium, Aspergillus and Bryssochamys. Previous literature reports have suggested that patulin is toxic to the immune system. The studies presented were conducted to provide a comprehensive assessment of the effects of patulin on the immune system. Unlike previous reports, the doses of patulin used (0.08, 0.16, 0.32, 0.64, 1.28 and 2.56 mg/kg) were based on predicted human exposure levels. Female B6C3F1 mice were exposed orally to patulin for 28 days. Effects were not observed on final body weight or body weight gain. Relative weight of the liver, spleen, thymus, kidneys with adrenals, and lungs was not affected. Peripheral blood leucocyte and lymphocyte counts were decreased by approximately 30% in the two highest dose groups. The leucocyte differential was not altered. Total spleen cell, total T-cell (CD3+), helper T-cell (CD4+CD8-), B-cell (surface immunoglobulin+) and monocyte (MAC-3+) counts were not changed. Cytotoxic T-cell (CD8+CD4-) counts were increased 50% only by the highest dose. Natural killer cell (NK1.1+CD3-) and monocyte (MAC-1+) counts were increased 30% and 24%, respectively, only in the 0.08 mg/kg group. Humoral immune function as assessed by antibody-forming cell response and serum IgM titre to sheep erythrocytes, and cell-mediated immune function evaluated utilizing natural killer cell activity and the mixed lymphocyte reaction were not altered. Oral exposure to patulin for 28 days did not alter the ability of female B6C3F1 mice to mount either a cell-mediated or humoral immune response.