Splenic NK Cell Activity Research Articles

Sex-specific effects of neonatal exposures to low levels of cadmium through maternal milk on development and immune functions of juvenile and adult rats

Cadmium (Cd) is a major environmental contaminant. Although immunotoxic effects have been associated with Cd exposure, the inconsistency of experimental results underlines the need of an experimental approach more closely related to environmental conditions. We investigated the effects of exposing neonatal Sprague–Dawley rats to environmentally relevant doses of Cd through maternal milk. Dams received 10 parts per billion (ppb) or 5 parts per million (ppm) Cd chloride (CdCl 2) in drinking water from parturition until the weaning of the pups. Half of the offspring was sampled at weaning time. The remaining juvenile rats received water without addition of Cd until adulthood. Cd accumulation in kidneys of juvenile rats fed from dams exposed to Cd indicated the transfer of the metal from mother to pups through maternal milk. This neonatal exposure resulted in decreased body, kidney and spleen weights of just weaned females but not of males. This effect was more pronounced in the less exposed females fed from dams exposed to 10 ppb Cd, which also displayed lower hepatic metallothionein-1 (MT-1) mRNA levels. The effect of Cd exposure on body and organ weights did not persist to adulthood. In contrast, we observed gender-specific effects of neonatal Cd exposure on the cytotoxic activity of splenic NK-cells of both juvenile and adult rats. Cd also strongly inhibited the proliferative response of Con A-stimulated thymocytes in both male and female adult rats 5 weeks after the cessation of Cd exposure. These immunotoxic effects were observed at doses much lower than those reported to produce similar effects when exposure occurred during adulthood. In conclusion, neonatal exposures to environmentally relevant levels of Cd through maternal milk represent a critical hazard liable to lead to both transitory and persistent immunotoxic effects.

Reduced splenic natural killer cell activity in rats with a hyperreactive dopaminergic system

Interactions between the nervous system and the immune system have been recognized as important regulatory processes in determining the activity of the immune response. We have previously shown that rats, which differ in the reactivity of the dopaminergic system (APO-SUS and APO-UNSUS rats), also differ in experimental metastasis formation and in susceptibility to autoimmunity. APO-SUS rats have a high response to administration of apomorphine and can be characterized as hyperdopaminergic, whereas their APO-UNSUS counterparts show low susceptibility to apomorphine and have a hypodopaminergic phenotype. In this study we investigated whether the decreased experimental metastasis formation of APO-SUS rats compared to APO-UNSUS rats is associated with higher natural killer cell activity in APO-SUS rats. Surprisingly, splenic NK cell activity of hyperdopaminergic APO-SUS female as well as male rats is significantly lower than NK cell activity of their hypodopaminergic APO-UNSUS counterparts. The reduced splenic NK activity of female APO-SUS rats is associated with lower percentages of NK cells in the spleen cell population. In contrast, male APO-SUS and APO-UNSUS rats show similar numbers of NK cells in the spleen. There was no difference in plasma dopamine levels between APO-SUS and APO-UNSUS rats and i.p. treatment of rats with the dopaminergic agonist quinpirole did not alter NK cell activity. In conclusion, our data demonstrate that differences in the reactivity of the dopaminergic system are associated with differences in splenic NK cell activity. Moreover, our data demonstrate that in this model lower splenic NK cell activity is not related to increased experimental lung metastasis formation.

Altered cutaneous immune parameters in transgenic mice overexpressing viral IL-10 in the epidermis.

IL-10 is a pleiotropic cytokine that inhibits several immune parameters, including Th1 cell-mediated immune responses, antigen presentation, and antigen-specific T cell proliferation. Recent data implicate IL-10 as a mediator of suppression of cell-mediated immunity induced by exposure to UVB radiation (280-320 nm). To investigate the effects of IL-10 on the cutaneous immune system, we engineered transgenic mice that overexpress viral IL-10 (vIL-10) in the epidermis. vIL-10 transgenic mice demonstrated a reduced number of I-A(+) epidermal and dermal cells and fewer I-A(+) hapten-bearing cells in regional lymph nodes after hapten painting of the skin. Reduced CD80 and CD86 expression by I-A(+) epidermal cells was also observed. vIL-10 transgenic mice demonstrated a smaller delayed-type hypersensitivity response to allogeneic cells upon challenge but had normal contact hypersensitivity to an epicutaneously applied hapten. Fresh epidermal cells from vIL-10 transgenic mice showed a decreased ability to stimulate allogeneic T cell proliferation, as did splenocytes. Additionally, chronic exposure of mice to UVB radiation led to the development of fewer skin tumors in vIL-10 mice than in WT controls, and vIL-10 transgenic mice had increased splenic NK cell activity against YAC-1targets. These findings support the concept that IL-10 is an important regulator of cutaneous immune function.

Altered cutaneous immune parameters in transgenic mice overexpressing viral IL-10 in the epidermis

IL-10 is a pleiotropic cytokine that inhibits several immune parameters, including Th1 cell-mediated immune responses, antigen presentation, and antigen-specific T cell proliferation. Recent data implicate IL-10 as a mediator of suppression of cell-mediated immunity induced by exposure to UVB radiation (280-320 nm). To investigate the effects of IL-10 on the cutaneous immune system, we engineered transgenic mice that overexpress viral IL-10 (vIL-10) in the epidermis. vIL-10 transgenic mice demonstrated a reduced number of I-A(+) epidermal and dermal cells and fewer I-A(+) hapten-bearing cells in regional lymph nodes after hapten painting of the skin. Reduced CD80 and CD86 expression by I-A(+) epidermal cells was also observed. vIL-10 transgenic mice demonstrated a smaller delayed-type hypersensitivity response to allogeneic cells upon challenge but had normal contact hypersensitivity to an epicutaneously applied hapten. Fresh epidermal cells from vIL-10 transgenic mice showed a decreased ability to stimulate allogeneic T cell proliferation, as did splenocytes. Additionally, chronic exposure of mice to UVB radiation led to the development of fewer skin tumors in vIL-10 mice than in WT controls, and vIL-10 transgenic mice had increased splenic NK cell activity against YAC-1targets. These findings support the concept that IL-10 is an important regulator of cutaneous immune function.

Enhanced Recovery of NK Cell Activity in Mice under Restraint Stress by the Administration of a Biological Response Modifier Derived from the Mycelia of the Basidiomycete Tricholoma matsutake

Some types of stressor act on the immune system via the network comprising the endocrine-immune-nervous systems, and are reportedly responsible for the onset of diseases as well as giving impetus to their advance. It is important for the maintenance and promotion of health to cope with stress-induced changes in immunocompetence. Therefore, we studied the effects of administration of a novel biological response modifier (CM6271) derived from the mycelia of the basidiomycete Tricholoma matsutake on the NK cell activity in mice under restraint stress, in order to evaluate its potential to modulate immune responsiveness in stress-loaded individuals. (1) When C57BL/6 mice were restrained in 50-ml tubes for more than 6 h, splenic NK cell activity decreased significantly, but recovered gradually after the mice were released. The extent of the reduction of activity and the degree of recovery depended on the duration of the restraint. (2) The oral administration of CM6271 caused a significant acceleration of the recovery of the activity. This effect was dependent on the timing of administration and the dose given. (3) The administration of CM6271 had no clear effect on the blood levels of ACTH, corticosterone or lipid peroxide levels in the liver. These findings suggest that CM6271 promotes recovery from the decrease in NK cell activity induced by restraint stress.

DIFFERENTIAL STAT5 ACTIVATION AND PHENOTYPIC MARKER EXPRESSION BY IMMUNE CELLS FOLLOWING LOW LEVELS OF ETHANOL CONSUMPTION IN MICE

ABSTRACTEthanol has been recognized as an immunosuppressive agent for many years. Effects of high levels of ethanol consumption on immune functions have been extensively studied, but little is known about the effects of low levels (scuh as 5% ethanol) of ethanol consumption. Herein we report that exposure of mice to 5% ethanol for 4–8 weeks decreases IL-2-augmented splenic NK cell activity, decreases the numbers of NK cells in spleen and liver, decreases the number of granulocytes (Gr-1+) in bone marrow and spleen, and decreases the percentages of B cells in liver. In contrast, the percentages of CD4+CD8+ thymocytes, CD4+CD8− splenocytes, CD4+CD8− liver nonparenchymal cells, CD3+ splenocytes, and CD3+ bone marrow cells were increased. Furthermore, exposure to 5% ethanol increases STAT5 activation in T cells and liver cells while decreases STAT5 activation in NK cells. Taken together, these findings suggest that low levels of ethanol consumption can differentially modulate immune cells in thymus, spleen, bone marrow and liver, which may be due to differential regulation of STAT5 activation by ethanol.

Chronic ethanol inhibits NK cell cytolytic activity: role of opioid peptide beta-endorphin.

The role of beta-endorphin (beta-EP) in ethanol-altered NK cell cytolytic activity is studied using male Fischer-344 rats as an animal model. Ethanol was administered for 1, 2, 3, or 4 wk in a liquid diet containing 8.7% ethanol (v/v), which means that 37% of the total calories were derived from ethanol. Rats treated with ethanol for 1 wk showed an increase in hypothalamic and plasma levels of immunoreactive (IR)-beta-EP, but displayed no significant effect on NK cell activity determined by (51)Cr release assay, as compared with those in pair-fed and ad libitum-fed animals. However, animals treated with ethanol for 2, 3, or 4 wk showed decreased hypothalamic and plasma levels of IR-beta-EP and decreased splenic NK cell activity. No significant decrease in the number of splenocytes and NK cells or in the percentage of NK cells was seen until after 3 and 4 wk of ethanol treatment. Exposure in vitro of splenic lymphocytes obtained from control animals to various concentrations of beta-EP increased NK cell activity. The opiate antagonist naltrexone blocked the beta-EP-stimulated effect. The in vitro NK cell response to beta-EP was reduced in the splenocytes obtained from animals treated with ethanol for 2 wk, but not in those obtained from animals treated with ethanol for 1 wk as compared with those in control animals. Additionally, beta-EP administration into the paraventricular nucleus of the hypothalamus stimulated NK cell cytolytic activity, whereas the opiate blocker administration reduced NK cell activity. The NK cell responses to paraventricular nucleus beta-EP were reduced in the animals treated with ethanol for 2 wk. These data provide evidence for the first time that ethanol inhibits NK cell cytolytic activity, possibly by reducing beta-EP-regulated splenic NK cell function.

Modulating immune responses with probiotic bacteria.

For many years, probiotic bacteria have been known to confer health benefits to the consumer. One possible mechanism for this may be the ability of probiotic bacteria to modulate immune responses. Oral administration of Lactobacillus casei strain Shirota (LcS) has been found to enhance innate immunity by stimulating the activity of splenic NK cells. Oral feeding with killed LcS was able to stimulate the production of Th1 cytokines, resulting in repressed production of IgE antibodies against Ovalbumin in experimental mice. The ability to switch mucosal immune responses towards Th1 with probiotic bacteria provides a strategy for treatment of allergic disorders. Growth of Meth A tumour cells in the lungs was also inhibited by intrapleural injection of LcS. Oral administration of other probiotic bacteria, such as Streptococcus thermophilus (St), Lactobacillus fermentum (Lf) and yeast (Y), elicited different immune responses. Mice that were prefed yeast or Lf followed by feeding with ovalbumin (OVA) responded better to vaccination with OVA than mice not given either probiotic or OVA or mice that had been prefed only OVA. However, antibody responses were significantly suppressed in response to vaccination with OVA in mice that had been prefed yeast followed by yeast and OVA as well as mice prefed Lf followed by Lf and OVA. Prefeeding St followed by OVA feeding enhanced cellular immune responses against ovalbumin. In contrast, mice prefed St followed by St + OVA were hyporesponsive against OVA. While antigen feeding alone appears to prime for an immune response, cofeeding antigen with probiotic bacteria can suppress both antibody and cellular immune responses and may provide an efficacious protocol to attenuate autoimmune diseases, such as experimental allergic encephalomyelitis, by jointly dosing with myelin basic protein and probiotic bacteria.

The impact of age, gender, and sex steroids on psychological and endocrine responses to psychosocial stress and DEX-CRF in healthy elderlies and young controls: Findings in three placebo controlled double blind studies

The effects of the timing of stressor application on transplanted tumor cells and its possible regulation by an immunomodulator was investigated. Male C57 BL/6N mice were subjected to rotational stressor for 7 days relative to tumor cell inoculation: stressor after inoculation of Lewis lung cancer cells, stressor during inoculation and stressor before inoculation. Stressor application and tumor cell inoculation induced transient decreases in body weight, particularly in mice stressed after inoculation. The mice exposed to the stressor during inoculation or before inoculation showed significant increases in the number of metastatic foci relative to control mice. Early administration of an immunomodulator, PSK, significantly attenuated the increase of metastatic foci in stressed mice. The weights of thymus gland and spleen at 14 days after inoculation were similar in the three stressor groups and the control group. Application of the stressor reduced NK cell activity of the normal mice as well as tumor bearing mice. The lowest pre-inoculation NK cell activity was observed in mice stressed for 7 days beginning on the day of inoculation. The NK cell activity decreased in the tumor bearing mice which were stressed at the time of tumor inoculation. Decreased NK cell activity was reversed at day 14 after tumor inoculation. The mice exposed to the stressor after inoculation showed lowest level of NK cell activity relative to mice exposed to the stressor before or during inoculation. The treatment of mice with PSK reduced these changes significantly. The present results suggest that the rotational stress reduces splenic NK cell activity, which may influence the magnitude of tumor metastasis, depending on the time of tumor cell injection. Further, administration of an immunomodulator may counteract the reduction of the NK cell activity.

Time-dependent effects of stressor application on metastasis of tumor cells in the lung and its regulation by an immunomodulator in mice.

The effects of the timing of stressor application on transplanted tumor cells and its possible regulation by an immunomodulator was investigated. Male C57 BL/6N mice were subjected to rotational stressor for 7 days relative to tumor cell inoculation: stressor after inoculation of Lewis lung cancer cells, stressor during inoculation and stressor before inoculation. Stressor application and tumor cell inoculation induced transient decreases in body weight, particularly in mice stressed after inoculation. The mice exposed to the stressor during inoculation or before inoculation showed significant increases in the number of metastatic foci relative to control mice. Early administration of an immunomodulator, PSK, significantly attenuated the increase of metastatic foci in stressed mice. The weights of thymus gland and spleen at 14 days after inoculation were similar in the three stressor groups and the control group. Application of the stressor reduced NK cell activity of the normal mice as well as tumor bearing mice. The lowest pre-inoculation NK cell activity was observed in mice stressed for 7 days beginning on the day of inoculation. The NK cell activity decreased in the tumor bearing mice which were stressed at the time of tumor inoculation. Decreased NK cell activity was reversed at day 14 after tumor inoculation. The mice exposed to the stressor after inoculation showed lowest level of NK cell activity relative to mice exposed to the stressor before or during inoculation. The treatment of mice with PSK reduced these changes significantly. The present results suggest that the rotational stress reduces splenic NK cell activity, which may influence the magnitude of tumor metastasis, depending on the time of tumor cell injection. Further, administration of an immunomodulator may counteract the reduction of the NK cell activity.

Effects of l-deprenyl treatment on noradrenergic innervation and immune reactivity in lymphoid organs of young F344 rats

Sympathetic noradrenergic (NA) neuronal activities in the thymus, spleen and mesenteric lymph nodes (MLN) and immune responses in the spleen were examined in young male F344 rats treated daily with 0, 0.25 mg, or 2.5 mg/kg body weight of l-deprenyl, an irreversible monoamine oxidase-B (MAO-B) inhibitor. Rats were treated daily for 1, 15, or 30 days, and sacrificed 7 days after the last deprenyl treatment. Deprenyl treatment increased norepinephrine (NE) content in the spleen without modifying the pattern and density of NA innervation in the splenic white pulp. The concentration of NE was unaltered in the thymus, but it was increased in the MLN of deprenyl-treated rats. One day of treatment with deprenyl decreased splenic NK cell activity while 15 days of deprenyl treatment enhanced splenic NK cell activity. Deprenyl elevated Con A-induced T lymphocyte proliferation following 30 days of treatment, but did not alter spleen cell Con A-induced IL-2 production or the percentage of CD5+ T cells in the spleen. A moderate decrease in the percentage of sIgM+ B cells was observed in the spleens of 15- and 30-day deprenyl-treated rats. These results suggest that deprenyl has sympathomimetic action on sympathetic NA nerve fibers in the spleen; the enhancement of NA neuronal activity may contribute to the modulation of immune responses in the spleen.

Ethanol-induced activation of the hypothalamic-pituitary-adrenal axis in a mouse model for binge drinking: Role of Ro15-4513-sensitive gamma aminobutyric acid receptors, tolerance, and relevance to humans

A mouse model for binge drinking has been developed in this laboratory, and several aspects of this model have been characterized. Many of the immunosuppressive effects of ethanol (EtOH) in this model seem to be mediated by activation of the hypothalamic-pituitary-adrenal (HPA) axis and consequent increases in the concentration of glucocorticoids, catecholamines, and perhaps other immunosuppressive mediators. The purpose of the work described here is to examine three important issues regarding the EtOH-induced neuroendocrine response in this model: 1) Are Ro15-4513-sensitive gamma aminobutyric acid type A (GABA-A) receptors involved in activation of the HPA axis by EtOH? 2) Does daily administration of EtOH produce tolerance with regard to activation of the HPA axis or with regard to suppression of natural killer cell activity? 3) Is the HPA axis activated by similar blood EtOH concentrations in humans and in the mouse model? Ro15-4513, a partial inverse agonist of GABA-A receptors, did not affect EtOH-induced increases in blood corticosterone levels. This suggests that Ro15-4513-sensitive GABA-A receptors are not involved in EtOH-induced activation of the HPA axis and that inhibition of corticosterone production is not the mechanism by which Ro-15-4513 blocks EtOH-induced immunosuppression. To evaluate tolerance, mice were given a daily dose of EtOH (6.5 g/kg by gavage) or vehicle (water) for 10 days. Control groups received vehicle or EtOH only on the last day of the experiment. At the optimum time after EtOH administration serum corticosterone and splenic NK cell activity were measured. The results indicate no significant alterations in the response to EtOH of mice exposed to EtOH for 10 days compared to those exposed only once. To compare the HPA axis response of mice and humans, lower EtOH dosages than generally used in our model were administered to mice, and the corticosterone response was compared to published data for humans who had similar ranges of blood EtOH levels. The results suggest that humans and mice exhibit activation of the HPA axis only when blood EtOH levels exceed ~0.14%. Together these results further characterize a mouse model for binge drinking that seems to provide a reasonable representation of many aspects of binge drinking in humans.

Role of central opioid receptor subtypes in morphine-induced alterations in peripheral lymphocyte activity

Morphine has been shown to decrease proliferative responses of rat T-lymphocytes via central opioid receptors, however, the specific receptor subtype(s) mediating this effect have not been established. To determine the potential role of central μ opioid receptors in morphine-mediated suppression of T-lymphocyte proliferation, 20 nmol/2 μl of either morphine sulfate or DAMGO ( μ-selective agonist) were administered into the lateral ventricle of freely moving Sprague–Dawley rats. Lymphocyte proliferative response to the polyclonal T cell mitogen concanavalin A (ConA), changes in splenic natural killer cell (NK) cytolytic activity, activation of the hypothalamic–pituitary–adrenal (HPA) axis and antinociception (tail-flick latency) were examined. Results indicated that like morphine, DAMGO decreased blood lymphocyte proliferative responses by 80% and elevated both tail-flick latency and plasma corticosterone when compared to saline-treated animals. The proliferation response of lymphocytes from the spleen or thymus and splenic NK cell activity were not significantly altered by either morphine or DAMGO treatment. The effects of DAMGO were determined to be dose-dependent and completely antagonized by naltrexone pretreatment. Central administration of DPDPE ( δ-selective agonist) and U-50488 ( κ-selective agonist) produced between 40–50% suppression of blood lymphocyte proliferation responses only at a dose five times greater (100 nmol) than DAMGO treatment, without altering antinociception or activation of the HPA axis. To determine the central opioid receptor subtype(s) involved in the effects of morphine, selective opioid antagonists were microinjected into the lateral ventricle prior to morphine treatment (6 mg/kg, s.c.). CTOP ( μ-selective antagonist, 5 μg/2 μl) completely blocked the effects of morphine on all parameters measured, however, naltrindole ( δ-selective antagonist, 2 μg/2 μl) or nor-binaltorphimine ( κ-selective antagonist, 73.5 μg/2 μl) failed to block the effects of morphine. Collectively, these results provide evidence that morphine acts primarily through central μ receptors to modulate peripheral blood lymphocyte proliferation responses. Further, the antinociception and blood lymphocyte effects show greater sensitivity to opioids than either natural killer cell cytolytic activity or activation of the HPA axis.

Alpha interferon administration paradoxically inhibits the development of diabetes in BB rats

Alpha-interferon (IFN-α) is thought to be important in the pathogenesis of insulin dependent diabetes mellitus (IDDM). However, since potent inducers of IFN-α, viruses, have been shown to modulate immune function and autoimmunity, we investigated whether administration of recombinant IFN-α (rIFN-α) would inhibit the diabetic process in BB rats. The development of diabetes was significantly inhibited by injections of either 10 5 units or 4 × 10 5 units rIFN-α. rIFN-α was more effective in preventing disease when injections were initiated at an earlier age (28–30 days vs 35–40 days). Histologic examination revealed a markedly lower degree of insulitis in rIFN-α treated rats. The mean total peripheral WBC and differential count, T-cell subsets, peripheral blood NK cell number, splenic NK cell activity, and serum cytotoxic beta cell surface antibody levels were unaltered by rIFN-α administration. In vitro incubation with rIFN-α inhibited the Con A proliferative response of mononuclear splenocytes of BB rats but not of Sprague Dawley rats. These results document that rIFN-α treatment potently prevents diabetes by inhibiting the development of insulitis. This paradoxical diabetes sparing effect may have significant implications for the treatment and prevention of IDDM and towards the understanding the autoimmune process.

Immunomodulation mediated by microinjection of morphine into the periaqueductal gray matter of the mesencephalon.

Opioids such as morphine have profound suppressive effects on the immune system. Many studies have shown that the immunocompetence of macrophages, NK cell activity, and T and B lymphocyte functions are altered following administration of opioid agonists(1-6) There is growing evidence suggesting that there exists a complex, bidirectional link between central nervous system (CNS) and immune system(7). Elucidation of the mechanism(s) through which central opioid system induces immunosuppression is complicated by multiple communicative pathways among the nervous, endocrine and immune systems. It has been proved that the opioid receptors(3, 8-11) specifically e, but not δ or K receptors in the CNS(12, 13) play an important role in morphine-induced immunosuppression. The periaqueductal gray (PAG) matter of the mesencephalon has been reported to be one of the primary neural foci for the action of centrally administered morphine in eliciting the suppression of splenic NK cell activity(3). This immunosuppression has been hypothesized to be due to the activation of the hypothaiamic-pituitary-adrenal (HPA) axis or the sympathetic nervous system (SNS) or both(3, 14). Although it has long been known that the PAG is involved in regulation of many physiological functions including pain, fear and anxiety, autonomic regulation, vocalization and lordosis, aggressive behavior, reproductive behavior as well(15), the relationship between the PAG and the immunity is still unclear. This chapter will document the current knowledge of the effects of morphine microinjected into the PAG on neuroendocrine and immune systems.

Time-Dependent Differential Changes of Immune Function in Rats Exposed to Chronic Intermittent Noise

Noise is a highly relevant environmental and clinical stressor. Compared to most other experimental stressors, noise is a modest activator of neuroendocrine pathways that mimic the situation in human health where neuroendocrine activation by environmental stressors is often absent or difficult to establish. Little is known about the effects of noise exposure on the immune system. In the present work, the effects of a low-intensity chronic intermittent unpredictable noise regimen on various parameters of immune function was studied. Male wistar rats were exposed to a randomized noise protocol (white noise, 85 dB, 2–20 kHz) for 10 h per day, 15 min per h over a total period of 3 weeks. Control animals were exposed to ambient sound only. Immune function was monitored after 24 h, 7 days, and 21 days of noise exposure. Noise induced several significant changes in immune function in a time-dependent differential pattern involving both immunosuppression and immunoenhancement. After 24 h, serum IgM levels were increased and peripheral phagocytic activity was decreased. Splenic lymphocytic proliferation to mitogens was significantly decreased after 7 days, but slightly elevated after 3 weeks. The activity of splenic NK cells was increased significantly after 24 h and 7 days, but suppressed after 3 weeks. These results show that various parameters of immune function are affected differentially over time in a period of chronic mild noise stress, possibly due to sequential activation of different physiological mechanisms.

IL-12 is a central mediator of acute graft-versus-host disease in mice.

Distinct forms of graft-vs-host disease (GVHD) occur in (C57B1/6 x DBA/2)F1 (BDF1) mice inoculated with either C57B1/6 or DBA/2 parental spleen cells, and it has been suggested that this reflects differential activation of CD4+ Th cell subsets. Transfer of B6 cells produces an acute GVHD, during which an early period of lymphoid hyperplasia precedes immunosuppression, weight loss, and mortality, and a Th1 pattern of cytokines is produced. Conversely, transfer of DBA/2 cells induces a chronic GVHD, in which no weight loss or mortality is observed, but an autoimmune, SLE-like GVHD develops in association with a Th2 pattern of cytokines. Recent work indicates that IL-12 plays a central role in the polarization of Th cell-dependent responses, and here we have examined its role in polarizing GVHD, by administering or depleting IL-12 during the afferent phase of both the acute and chronic forms of GVHD in BDF1 mice. In vivo neutralization of endogenous IL-12 ameliorated acute GVHD, in association with reduced splenic NK cell activity, IFN-gamma production, immunosuppression, weight loss, and mortality. Conversely, administration of exogenous murine rIL-12 exacerbates this disease and converts the chronic GVHD into a lethal acute GVHD-like syndrome. These results indicate that IL-12 plays an important role in the development of acute, but not chronic, GVHD and suggest that differential production of IL-12 early in the disease may underlie these distinct outcomes of the GVHD in BDF1 mice injected with different parental cells.

Tolerance and crosstolerance to the suppressive effects of cocaine and morphine on lymphocyte proliferation

The effects of acute or daily exposure to either cocaine or morphine on lymphocyte proliferative responses and NK cytolytic activity were determined. Two hours following the IV infusion of cocaine (5 mg/kg), blood lymphocyte proliferative responses were found to be suppressed by 75%. Cocaine had no effect on proliferative responses of thymic or splenic lymphocytes or cytolytic activity of splenic NK cells following acute or 5-day repetitive dosing. Similar to the effects of cocaine, morphine (10 mg/kg) administration was also accompanied by a suppressed blood lymphocyte response, which was no longer apparent 8 days following repeated morphine injections. Animals that had received daily injections of either morphine of cocaine were also found to be resistant to the inhibitory effects of a single dose of morphine or cocaine, respectively. These data suggest repeated exposure to either morphine or cocaine results in the development of an apparent crosstolerant state to further suppression of blood lymphocyte proliferative responses by either drug.

T cell receptor V beta complementarity-determining region 1 peptide administration moderates immune dysfunction and cytokine dysregulation induced by murine retrovirus infection.

Murine AIDS, induced by LP-BM5 murine leukemia retrovirus infection, causes a progressive and profound immunodeficiency in female C57B1/6 mice. Previously, we reported that autoantibodies were elevated during the initiation phases of this murine retrovirus infection and bound peptide determinants corresponding to CDR1 of several TCR V beta-chains. Therefore, we designed studies to determine whether administration of a major autoimmunogenic TCR V beta CDR1 peptide before or after infection with LP-BM5 retrovirus would modulate retrovirus-induced dysregulation of T cell function. Administration of the TCR V beta CDR1 peptide before murine retrovirus infection significantly prevented its suppression of splenic NK cell activity, T and B cell proliferation, and monokine (IL-6 and TNF-alpha) and Th1 cytokine (IL-2 and IFN-gamma) release by splenocytes, and inhibited retrovirus-induced elevation of Th2 cytokine (IL-5 and IL-10). Similar data were obtained with peptide immunization 2 wk after murine retrovirus infection at 6 and 16 wk postinfection. However, delaying peptide immunization until severe suppression of T and B cell mitogenesis had occurred did not restore their functions. Immunization with TCR V beta peptide prevents development of retrovirus-induced immune dysfunction, which suggests a possible pathogenic role of autoreactive T cells as regulatory elements.

Heterogeneity of natural killer cell subsets in NK-1.1 + and NK-1.1 − inbred mouse strains and their progeny

The 4LO3311 monoclonal antibody, a new NK-specinc reagent recently produced in our laboratory, reacts with spleen cells of 11 mouse strains, most of which do not express the NK-1.1 alloantigen recognized by the PK136 mAb. Among positive strains, the susceptibility of spleen cells to the complement-dependent NK-inhibiting activity of the 4LO3311 mAb was variable but independent of the initial NK cell activity level of cells tested. This property was furthermore not modified after poly(I:C) stimulation. The susceptibility of spleen cells to the in vitro 4LO3311 mAb plus complement treatment is however influenced by the absolute number of 4LO3311 + cells as well as by the density of the corresponding alloantigen at the cell surface. Moreover, it was established that the strain-related variations observed also depended upon the relative size of the 4LO3311 cell subset within the lytic NK cell population. Indeed, when C3H (NK-1.1 −4LO3311 +) mice were inoculated with the 4LO3311 mAb, the lytic activity of their spleen cells was almost unaltered but 4LO3311-reactive cells were no longer detected in the spleen of treated animals and remaining NK cells were totally resistant to the in vitro 4LO3311 mAb plus complement treatment. These findings indicate that the 4LO3311 mAb identifies a subset rather than all NK cells, even in a NK-1.1 − strain. Since a NK-1.1-unreactive cell subset was identified in NZB (NK-1.1 +4LO3311 −) mice inoculated with the PK136 mAb, the NK-1.1 + cell population is not necessarily responsible for all the splenic NK cell activity in all NK-1.1 + strains. In B6C3F 1 hybrid mice, a relatively large subset of NK-1.1 −4LO3311 − cells was found in addition to those expressing the NK-1.1, the 4LO3311 alloantigen, or both. According to these results, NK cell heterogeneity should thus be taken as an evolving concept whose resolution appears more and more complex with the identification of new NK-specific reagents.