Lee S.F. Soderberg

The effect of prenatal chlordane exposure on the delayed hypersensitivity response of BALB/c mice

Previous studies in our laboratory have indicated that in utero chlordane exposure caused a significant enhancement in the survival of the offspring to influenza virus infection. Further studies, reported here, show that the non-specific delayed type hypersensitivity (DTH) response to oxazolone at 100 days of age, but not at 30 days of age, was significantly depressed. In contrast, the Con A-induced blastogenic response of spleen cells from chlordane-treated offspring was not depressed and was, in fact, significantly enhanced. However, neither the response to PHA nor to LPS mitogens was significantly altered. In utero exposure to chlordane significantly depressed the mixed lymphocyte reactivity (MLR) of spleen cells from male offspring, whereas females showed no significant alteration of MLR. The significant depression of the DTH and MLR responses supports our previous reports of enhanced survival of influenza virus infection following in utero exposure to chlordane, since active DTH contributes to the pathology of influenza virus infection in mice. The normal or enhanced T-cell mitogen response suggested that the chlordane-induced depression of DTH and MLR was not due to overt toxicity to T-cells.

The effect of in utero exposure to hexachlorobenzene on the developing immune response of BALB/c mice.

BALB/c mice were exposed to 0.0, 0.5 and 5.0 mg/kg maternal body weight hexachlorobenzene (HCB) throughout gestation by daily per os dosing of the females. At 45 days of age selected immune functions of the offspring were assessed. The delayed-type hypersensitivity (DTH) response to oxazolone was severely depressed in animals exposed to either 0.5 or 5.0 mg/kg HCB, however, only those animals exposed to 5.0 mg/kg HCB showed a significant decrease in their mixed lymphocyte response (MLR) levels. The ability of isolated spleen cells to undergo a blastogenic response to concanavalin A (ConA), phytohemagglutinin (PHA) and lipopolysaccharide (LPS) showed no significant changes due to HCB exposure. Similarly, no significant difference in the induction of direct hemolytic plaque-forming cells was seen. A significant increase in the relative distribution of splenic T cells and a significant decrease in splenic B cells was measured in the offspring of HCB-treated females. These results suggest that HCB is capable of affecting the development or maturation of the immune response in mice, perhaps at the T cell level.

T cell functions are impaired by inhaled isobutyl nitrite through a T-independent mechanism

Isobutyl nitrite is representative of a group of inhalants abused by male homosexuals and adolescents. Inhalation exposure of mice to isobutyl nitrite at 900 ppm for 45 min per day for 14 days caused serious deficits in T cell-mediated immune responses. Cytotoxic T lymphocyte (CTL) activity was reduced by 36% following the exposure. T cell proliferative responses to mitogenic and allogeneic stimulation were reduced by 37% and 51%, respectively. The exposure did not directly alter the ability of cells to synthesize or respond to IL-2. Accessory cell function in facilitating T cell activation was inhibited by about 50% following exposure to the inhalant.

Transforming growth factor-β is the major mediator of natural suppressor cells derived from normal bone marrow

We previously reported that murine bone marrow cells activated by interleukin‐3 (IL‐3) or granu‐ locyte‐macrophage colony‐stimulating factor (GM‐CSF) had potent nonspecific natural suppressor (NS) cell activity. In the present study, we demonstrated that these activated NS cells released a soluble factor (or factors) capable of nonspecifically inhibiting T cell mitogenic responses. Consistent with the properties of Transforming growth factor‐β (7GF‐β), treatment of the NS supernates with heat failed to denature the factor, and in fact significantly increased its suppressive activity. The NS suppressor factor strongly inhibited proliferation of the TGF‐ β‐sensitive tumor cell line, A549. Cytokine activation of suppressive activity correlated with the production of a 10‐ to 13‐kDa protein, consistent with the size of TGF‐β and rIL‐3 induced a sevenfold increase in TGF‐β transcription. Finally, neutralizing anti‐TGF‐β antibody inhibited the suppressive activity of the supernates, indicating that TGF‐β was responsible for most, if not all, of the suppression expressed by these bone marrow NS cells.

Influenza type a virus infection of mice exposed in utero to chlordane; survival and antibody studies

Previous studies carried out by others have shown that in utero exposure of mice to chlordane effects a significant depression of cell-mediated immunity (CMI) at 100 days of life without adversely affecting the humoral immune system. In the studies reported herein we assessed the effect of in utero exposure to various doses of chlordane on the response of 38-day-old mice to influenza type A virus infection in terms of relative levels of mortality, mean day of death, and the levels of antiviral antibody in the primary and secondary immune response to the virus. In utero exposure to chlordane effected enhanced survival to influenza type A virus infection relative to mock-treated animals. No significant differences were noted in the mean day of death of chlordane-treated and mock-treated mice. A significant enhancement in the levels of antiviral antibody was noted in the chlordane-treated female mice but not male mice in both the primary and secondary immune response to the virus.

Inhalation exposure to isobutyl nitrite inhibits macrophage tumoricidal activity and modulates inducible nitric oxide.

Abuse of nitrite inhalants is common among male homosexuals and a history of abuse has been correlated with seropositivity to HIV and with the incidence of Kaposis sarcoma among AIDS patients. The present study shows that inhalation exposure of mice to 900 ppm isobutyl nitrite for 45 min/day for 14 days compromised macrophage tumoricidal activity by up to 40% and it remained compromised for at least 7 days after terminating exposures. The inhalation exposures did not affect tumor cell binding but did inhibit inducible nitric oxide (NO•). The NO• synthase inhibitor NG‐methyl‐l‐arginine totally inhibited both NO• production and cytotoxicity, suggesting that reductions in NO• due to inhalant exposure may be responsible for the reduced cytotoxic activity. Exposure to the inhalant increased constitutive production of tumor necrosis factor‐α (TNF‐α). TNF‐α has been reported to stimulate the replication of HIV and the proliferation of Kaposis sarcoma cells in vitro. J. Leukoc. Biol. 57: 135–140; 1995.

Radiation Protection and Radiation Recovery with Essential Metalloelement Chelates

Abstract Understanding essential metalloelement metabolism and its role in tissue maintenance and function, as well as the roles of essential metalloelement-dependent enzymes in responding to injury, offer a new approach to decreasing and/or treating radiation injury. This review presents the roles of some essential metalloelement-dependent enzymes in tissue maintenance and function, and their responses to radiation injury in accounting for radiation protection and recovery effects observed for nontoxic doses of essential metalloelement compounds. Effects of biochemicals including water undergoing bond radiolysis and the effects of free radicals derived from diatomic oxygen account for the acute and chronic aspects of radiation injury. Recognized biochemical roles of essential metalloelement-dependent enzymes and the observed pharmacological effects of small-molecular mass chelates predict the therapeutic usefulness of essential metalloelement complexes in decreasing and/or treatment of radiation injury. Copper chelates have radiation protection and radiation recovery activities and cause rapid recovery of immunocompetency and recovery from radiation-induced histopathology. Mice treated with Cu(II)2(3,5-dilsopropylsalicylate)4 [Cu (II)2(3,5-DIPS)4] had increased survival and corresponding increases in numbers of myeloid and multipotential progenitor cells early after irradiation and earlier recovery of immune reactivity. Examination of radiation-induced histopathology in spleen, bone marrow, thymus, and small intestine also revealed Cu(II)2(3,5-DIPS)4-mediated rapid recovery of radiation-induced histopathology. Most recently, Fe, Mn, and Zn complexes have also been found to prevent death in lethally irradiated mice. These pharmacological effects of essential metalloelement chelates can be understood as due to facilitation of de novo synthesis of essential metalloelement-dependent enzymes which have roles in preventing the accumulation of pathological concentrations of oxygen radicals or repairing biochemical damage caused by radiation-induced bond homolysis. Essential metalloelement chelates offer a physiological approach to prevention and/or treatment of radiation injury.

Cytokine regulation of bone marrow natural suppressor cell activity in the suppression of lymphocyte function

Natural suppressor (NS) cells, which nonspecifically suppress immune responses, are present in the spleen following exposure to radiation, chronic graft-versus-host disease, or cancer and in normal bone marrow. A model system is described which allows the study of cytokines activating and inhibiting NS cells, cytokines mediating NS activity, and NS effects on cytokine synthesis. Recombinant interleukin-3 (rIL-3) and granulocyte-macrophage colony-stimulating factor (rGM-CSF) efficiently activated NS cells present in normal bone marrow and were effective at concentrations as low as 5 U/ml. At high concentrations, GM-CSF, but not IL-3, did not activate NS cells. Recombinant interferon-gamma (rIFN-gamma) blocked the activation of bone marrow NS cells by rIL-3, but did not down-regulate NS cells once activated. The NS cells secreted one or more soluble suppressor factors, which blocked IL-2 synthesis and also inhibited IL-2-dependent T cell proliferation in the presence of excess IL-2.

Cytotoxic T-lymphocyte and NK responses in mice treated prenatally with chlordane.

It has been reported previously that BALB/c mice, treated in utero with chlordane, showed increased survival to influenza A/PR/8/34 [H1N1] (influenza) virus as young adults. To determine the possible role of cell-mediated immunity (CMI) on this effect, cytotoxic T-lymphocyte (CTL) and natural killer (NK) cell activities were assessed on chlordane-exposed offspring at 100 and 200 days post partum. The CTL response of these offspring showed no significant change from that obtained from their sex- and age-matched control counterparts exposed prenatally to the vehicle. NK responses of chlordane-exposed female offspring were significantly higher at 100 days of age but not at 200 days of age. Although male offspring that were exposed to chlordane prenatally showed no difference in NK cell activity at 100 days of age, NK cell activity was significantly less in chlordane-treated animals than controls at 200 days of age. Thus, prenatal treatment of mice with chlordane had varying effects on the NK cell activity of adult offspring, depending on the sex and age of the animal. It is concluded that the previously reported increase in survival to influenza is due to a resolution of the infection by normal CTL and NK cell activities coupled with a decrease in delayed-type hypersensitivity (DTH)-mediated pathology.

A soluble factor produced by bone marrow natural suppressor cells blocks interleukin 2 production and activity

We previously reported that a population of Fc gamma-receptor+ (Fc gamma R+) suppressor cells present in normal unstimulated rabbit bone marrow inhibited the growth of autologous rapidly proliferating bone marrow cells devoid of Fc gamma R. It is now reported that the Fc gamma R+ bone marrow cells produced a soluble, nondialyzable suppressor factor(s) (SF) which blocked the proliferation of Fc gamma R- bone marrow cells. In addition, the Fc gamma R+ cells and SF significantly inhibited spleen cell proliferation in response to concanavalin A (Con A), phytohemagglutinin, and pokeweed mitogen. The bone marrow SF exhibited a dose-dependent suppression of the growth of IL-2-dependent T lymphocytes in the presence of IL-2. SF also completely blocked the production or release of IL-2 by Con A-stimulated T cells. Thus, these bone marrow natural suppressor cells produced a soluble factor, which regulated the growth of rapidly proliferating bone marrow cells and also regulated T cell reactivity by modulating IL-2 production and activity.