Immunotoxicity of N,N-diethylaniline in mice: effect on natural killer activity, cytotoxic T lymphocyte activity, lymphocyte proliferation response and cellular components of the spleen

Natural Killer (NK) Cell Assays in Immunotoxicity Testing

It is well known that natural killer (NK) cells are involved in defense against viruses and some tumors. NK cells kill target cells by the directed release of cytolytic granules that contain perforin, granzymes, and granulysin. It is increasingly important to evaluate NK cell function in immunotoxicity testing. NK cell function can be evaluated by determining cytolytic activity against target tumor cells by the ⁵¹Cr-release assay and also by determining the number of NK cells in peripheral blood in humans and in the spleen in animals using flow cytometry. Recently, the intracellular levels of perforin, granzymes, and granulysin determined by flow cytometry have also been used in the evaluation of NK cell function. In addition, chemical-induced apoptosis in NK cells also has been applied to evaluate the immunotoxicity of chemicals. This chapter will describe the methods for NK cell assays in immunotoxicity testing.

Evaluation of Cell-Mediated Immune Function Using the Cytotoxic T-Lymphocyte Assay

Evaluation of cell-mediated immunity (CMI) is a significant component in any assessment designed to predict the full range of potential immunotoxic risk underlying health risks. Among measures of CMI, the cytotoxic T-lymphocyte (CTL) response is recognized as perhaps the most relevant functional measure that reflects cell-mediated acquired immune defense against viral infections and cancer. The CTL response against T-dependent antigens requires the cooperation of at least three different major categories of immune cells. These include professional antigen-presenting cells (e.g., dendritic cells), CD4⁺ T helper lymphocytes, and CD8⁺ T effector lymphocytes. It is also among the few functional responses dependent on and, hence, capable of evaluating effective antigen presentation via both class I and class II molecules of the major histocompatibility complex (MHC). For this reason, the CTL assay is an excellent candidate for evaluation of potential immunotoxicity. This chapter provides an example of a mouse CTL assay against influenza virus that has been utilized for this purpose.

Walnut Polyphenol Extract Attenuates Immunotoxicity Induced by 4-Pentylphenol and 3-methyl-4-nitrophenol in Murine Splenic Lymphocyte

4-pentylphenol (PP) and 3-methyl-4-nitrophenol (PNMC), two important components of vehicle emissions, have been shown to confer toxicity in splenocytes. Certain natural products, such as those derived from walnuts, exhibit a range of antioxidative, antitumor, and anti-inflammatory properties. Here, we investigated the effects of walnut polyphenol extract (WPE) on immunotoxicity induced by PP and PNMC in murine splenic lymphocytes. Treatment with WPE was shown to significantly enhance proliferation of splenocytes exposed to PP or PNMC, characterized by increases in the percentages of splenic T lymphocytes (CD3+ T cells) and T cell subsets (CD4+ and CD8+ T cells), as well as the production of T cell-related cytokines and granzymes (interleukin-2, interleukin-4, and granzyme-B) in cells exposed to PP or PNMC. These effects were associated with a decrease in oxidative stress, as evidenced by changes in OH, SOD, GSH-Px, and MDA levels. The total phenolic content of WPE was 34,800 ± 200 mg gallic acid equivalents/100 g, consisting of at least 16 unique phenols, including ellagitannins, quercetin, valoneic acid dilactone, and gallic acid. Taken together, these results suggest that walnut polyphenols significantly attenuated PP and PNMC-mediated immunotoxicity and improved immune function by inhibiting oxidative stress.

Effect of oral exposure to fenitrothion and 3-methyl-4-nitrophenol on splenic cell populations and histopathological alterations in spleen in Wistar rats

Fenitrothion (FNT) is used throughout the world as an insecticide in agriculture. To investigate the effect of FNT on the splenocytes and the underlying mechanism, FNT and its main metabolite, 3-methyl-4-nitrophenol (MNP), were administered orally to Wistar rats in daily doses of 0, 5 and 10 mg/kg, 4-5 days/week for 9 weeks. Splenocytes were harvested from control and exposed rats, and the following cell phenotypes were quantified by flow cytometry: (1) B cells (PE-CD45RA), (2) T cells (FITC-CD3), (3) T cell subsets (PE-CD4 and PerCPCD8), (4) natural killer (NK) cells (FITC-CD161a), (5) macrophages (FITC-CD11b), and (6) granulocyte (PE-granulocyte). Body weight, weight of the spleen, and histopathological alterations of spleens were also examined. The percentage of splenic CD8+ T cells and the ratio of CD8/CD4 in the group receiving 10 mg/kg FNT, and the percentages of splenic CD3+ and CD8+ T cells in the group receiving 10 mg/kg MNP were significantly decreased compared with those in the controls. FNT exposure also significantly decreased the weight of the spleen and body weight. In addition, apoptotic lymphocytes in spleen were observed in FNT-exposed rats under transmission electron microscope. However, FNT and MNP exposures did not affect splenic NK cells, B cells, macrophages, and granulocytes. The above findings indicate that FNT and MNP may selectively affect splenic T cells in rats.

The cytotoxic T lymphocyte assay for evaluating cell-mediated immune function

Evaluation of cell-mediated immunity (CMI) is a significant component in any assessment designed to predict the full range of potential immunotoxic risk underlying health risks. Among measures of CMI, the cytotoxic T Lymphocyte (CTL) response is recognized as perhaps the most relevant functional measure that reflects cell-mediated acquired immune defense against viral infections and cancer. The CTL response against T-dependent antigens requires the cooperation of at least three different major categories of immune cells. These include professional antigen presenting cells (e.g., dendritic cells), CD4(+) T helper lymphocytes, and CD8(+) T effector lymphocytes. It is also among the few functional responses dependent on and, hence, capable of evaluating effective antigen presentation via both class I and class II molecules of the major histocompatibility complex (MHC). For this reason the CTL assay is an excellent candidate for evaluation of potential immunotoxicity. This chapter provides an example of a mouse CTL assay against influenza virus that has been utilized for this purpose.

NK cell assays in immunotoxicity testing

It is well known that natural killer (NK) cells are involved in defense against viruses and some tumors. NK cells kill target cells by the directed release of cytolytic granules that contain perforin, granzymes, and granulysin. It is increasingly important to evaluate NK cell function in immunotoxicity testing. NK cell function can be evaluated by determining cytolytic activity against target tumor cells by the (51)Cr-release assay and also by determining the number of NK cells in peripheral blood in humans and in the spleen in animals using flow cytometry. Recently, the intracellular levels of perforin, granzymes, and granulysin determined by flow cytometry have also been used in the evaluation of NK cell function. This chapter will describe the methods for NK cell assays in immunotoxicity testing.

Ganoderma lucidum polysaccharides enhance the function of immunological effector cells in immunosuppressed mice

The present study was designed to determine in vivo efficacy of Ganoderma lucidum polysaccharides (Gl-PS) for enhancing the activity of immunological effector cells in immunosuppressed mice. Mice were injected intraperitoneally (i.p.) once daily with low-dose (2.5mg/kg), intermediate-dose (25mg/kg), and high-dose (250 mg/kg) of Gl-PS, respectively, for 7 consecutive days 24h after i.p. injection of a immunosuppressing anti-tumor agent cyclophosphamide (Cy, 300 mg/kg). In Cy-treated mice, compared to vehicle, low-dose Gl-PS accelerated recovery of bone marrow cells, red blood cells and white blood cells, as well as splenic natural killer cells and natural killer T cells, and enhanced T and B cell proliferation responses on day 8, cytotoxic T lymphocyte activity on day 5, as well as NK cell and lymphokine activated killer cell activity on days 7-9. Furthermore, it promoted phagocytosis and cytotoxicity of macrophages on day 12. The above beneficial effects induced by the low-dose Gl-PS treatment did not result in any side effects. These results demonstrate the efficacious effects of low-dose Gl-PS treatment for enhancing the activity of immunological effector cells in immunosuppressed mice, and may provide a basis for applying this herb as an efficacious adjacent immunopotentiating therapy against cancer chemotherapy-induced immunosuppression.

Dimethyl 2,2-dichlorovinyl phosphate (DDVP) markedly inhibits activities of natural killer cells, cytotoxic T lymphocytes and lymphokine-activated killer cells via the Fas-ligand/Fas pathway in perforin-knockout (PKO) mice

Natural killer (NK), lymphokine-activated killer (LAK) and cytotoxic T lymphocyte (CTL) cells induce target cell death by two main mechanisms, the perforin/granzyme pathway and the Fas-ligand (FasL)/Fas pathway. We have previously found that organophosphorus pesticides significantly inhibit human and murine NK, LAK and CTL activities and that this inhibition is partially mediated by the inhibition of granzymes. We asked here whether organophosphorus pesticides also affect the FasL/Fas pathway by using perforin-knockout (PKO) mice. Thus, we examined the effect that dimethyl 2,2-dichlorovinyl phosphate (DDVP), an organophosphorus pesticide has on NK, CTL and LAK activities of PKO mice in vitro using the Fas antigen-positive YAC-1 cell as a target in the present study. We found that DDVP significantly decreased NK, CTL and LAK activities in a dose-dependent manner, and that the CTL and LAK activities of PKO mice were significantly blocked by anti-FasL antibody, suggesting that DDVP and anti-FasL antibody have the same/similar mechanism of inhibiting LAK and CTL activities. We further found that DDVP decreases the expression of Fas antigen on YAC-1 cells, and the expression of FasL on LAK cells in a dose-dependent manner, respectively. Taken together, these findings indicate that the DDVP-induced inhibition of NK, LAK and CTL activities in PKO mice is mediated by the impairment of the FasL/Fas pathway.

Elevated frequency of sister chromatid exchanges of lymphocytes in sarin-exposed victims of the Tokyo sarin disaster 3 years after the event

We previously reported that the frequency of sister chromatid exchanges (SCEs) among victims of the Tokyo subway sarin disaster was significantly higher than that of controls 2-3 months after the disaster. It has been reported that the victims were also exposed to the by-products generated during sarin synthesis, i.e., diisopropyl methylphosphonate (DIMP), diethyl methylphosphonate (DEMP) and N,N-diethylaniline (DEA) during the disaster and we previously found that DIMP, DEMP and DEA induced a significant SCE increase in human lymphocytes in vitro. To monitor the genetic aftereffects of the sarin exposure, SCEs of peripheral blood lymphocytes were measured in fire fighters and police officers involved in the disaster 3 years after the event. We found that the frequency of SCEs was still significantly higher in the exposed subjects than the controls, suggesting a risk of the genetic aftereffects of the sarin exposure. We further found a significant positive correlation between the frequency of SCEs and the inhibition of serum cholinesterase activity in the exposed subjects, suggesting that the elevated frequency of SCEs is related to the sarin exposure. On the other hand, there was no significant difference in natural killer activity between the exposed and the controls.

Organophosphorus pesticides markedly inhibit the activities of natural killer, cytotoxic T lymphocyte and lymphokine-activated killer: a proposed inhibiting mechanism via granzyme inhibition

We have previously found that diisopropyl methylphosphonate, an organophosphorus by-product generated during sarin synthesis in the Tokyo sarin disaster, significantly inhibited natural killer (NK) and cytotoxic T lymphocyte (CTL) activities. In the present study, to investigate whether organophosphorus pesticides (OPs) also affect NK and CTL activities, we firstly examined the effect of five OPs on human NK activity, and then the effect of Dimethyl 2,2-dichlorovinyl phosphate (DDVP), an OP on murine splenic NK, CTL and lymphokine-activated killer (LAK), and human LAK activities in vitro. To explore the underlying mechanism of decreased NK activity, we also investigated the effect of 4-(2-aminoethyl) benzenesulfonyl fluoride-HCl (p-ABSF), an inhibitor of serine proteases on NK, LAK and CTL activities, and the effect of DDVP on the activity of granzymes (serine proteases). We found that OPs significantly decreased human NK activity in a dose-dependent manner, but the degree of decrease in NK activity differed among the OPs investigated, and that DDVP significantly decreased NK, LAK and CTL activities in a dose-dependent manner, but the degree of decrease in these activities differed. p-ABSF showed a similar inhibitory pattern to DDVP, and had an additive inhibitory effect with DDVP on NK, LAK and CTL activities. We also found that DDVP significantly inhibited granzyme activity in a dose-dependent manner. These findings indicate that OPs significantly decrease NK, LAK and CTL activities in vitro via granzyme inhibition.