Genetic susceptibility to progressive massive fibrosis in coal miners.

Progressive massive fibrosis (PMF) is a chronic interstitial lung disease with a complex aetiology that can occur after cumulative dust exposure. A case-control study was conducted to test the hypothesis that single nucleotide polymorphisms (SNPs) within genes involved in inflammatory and fibrotic processes modulate the risk of PMF development. The study population consisted of 648 underground coal miners participating in the National Coal Workers Autopsy Study, of which 304 were diagnosed with PMF. SNPs that influence the regulation of interleukin (IL)-1, IL-6, tumour necrosis factor-alpha, transforming growth factor-beta1, vascular endothelial growth factor (VEGF), epidermal growth factor intercellular cell adhesion molecule (ICAM)-1 and matrix metalloproteinase-2 genes were determined using a 5'-nuclease real-time PCR assay. There were no significant differences in the distribution of any individual SNP or haplotype between the PMF and control groups. However, the polygenotype of VEGF +405/ICAM-1 +241/IL-6 -174 (C-A-G) conferred an increased risk for PMF (odds ratio 3.4, 95% confidence interval 1.3-8.8). The present study suggests that the examined genetic variations that help regulate inflammatory and fibrotic processes are unlikely to strongly influence susceptibility to this interstitial lung disease, although the role of vascular endothelial growth factor, intercellular cell adhesion molecule-1 and interleukin-6 polymorphisms in the development of progressive massive fibrosis may require further investigation.

Antitumor activity of murine neutrophils demonstrated by cytometric analysis.

The cytostatic and cytolytic activities of activated polymorphonuclear neutrophils (PMNs) against YAC-1 lymphoma target cells were examined using multiparameter flow cytometric analysis. PMNs were resolved from tumor cells by 90 degrees light scatter. The number of surviving tumor cells was determined by adding a known concentration of fluorescent latex particles to the fixed cell suspension immediately prior to analysis and counting the particles simultaneously with the cells. Cell cycle progression of the YAC-1 target was studied by dual parameter analysis of DNA content and bromodeoxyuridine incorporation into tumor cell DNA either prior to or following addition of PMNs. The results indicate that activated PMNs effectively kill tumor cells within the first 24 h of coculture. However, between 24 and 48 h, tumor cells which escape destruction resume growth and eventually reach a growth rate greater than control cells.

Arsenic mediates cell proliferation and gene expression in the bladder epithelium: association with activating protein-1 transactivation.

Although the mechanism of action has not yet been defined, epidemiological studies have demonstrated an association between elevated arsenic levels in drinking water and the incidence of urinary bladder transitional cell carcinomas. In the current studies, we demonstrate that mice exposed to 0.01% sodium arsenite in drinking water develop hyperplasia of the bladder urothelium within 4 weeks of exposure. This was accompanied by the accumulation of inorganic trivalent arsenic, and to a lesser extent dimethylarsinic acid, in bladder tissue, as well as a persistent increase in DNA binding of the activating protein (AP)-1 transcription factor. AP-1 transactivation by arsenic also occurred in bladders of transgenic mice containing an AP-1 luciferase reporter. Consistent with these in vivo observations, arsenite increased cell proliferation and AP-1 DNA binding in a human bladder epithelial cell line. Gene expression studies using RNase protection assays, reverse transcription-PCR, and cDNA microarrays indicated that arsenite alters the expression of a number of genes associated with cell growth, such as c-fos, c-jun, and EGR-1, as well as cell arrest, such as GADD153 and GADD45. The proliferation-enhancing effect of arsenic on uroepithelial cells likely contributes to its ability to cause cancer.

Selective immunosuppression in mice of natural killer cell activity by ochratoxin A.

Ochratoxin A, a naturally occurring mycotoxin, has recently been shown to cause renal and hepatic carcinomas in mice. In the present studies, the effects of ochratoxin A on immune mechanisms associated with tumor resistance were examined in mice using dose levels similar to those that cause neoplasia. Ochratoxin A was shown to specifically inhibit natural killer (NK) cell activity and increase the growth of transplantable tumor cells without altering T-cell- or macrophage-mediated antitumor activity. In contrast, ochratoxin B, a much less toxic ochratoxin, did not influence immune function. Polyinosinic:polycytidylic induced interferon was markedly reduced in mice following exposure to ochratoxin A although total serum protein levels were slightly increased. Injection of polyinosinic:polycytidylic enhanced NK activity in the presence of ochratoxin A, although the level of enhancement was slightly lower than that produced by the agent in the absence of ochratoxin A. Thus, ochratoxin appears to suppress NK cell activity by inhibiting production of basal interferon. Additionally, these findings suggest a possible role for altered NK cell function in the development of mycotoxin-induced carcinogenesis.

Metabolic characterization of mouse bone marrow cells responsive to estrogenic inhibition: hexose monophosphate shunt enzyme activity in enriched populations of mature cells and progenitor cells.

Compounds with estrogenic activity cause initial toxic responses in the bone marrow characterized by hypocellularity and stem cell myelotoxicity. To elucidate the biochemical nature of these toxic responses, bone marrow cells were collected from mice treated with pharmacological doses of estrogenic chemicals, separated into enriched cell populations, and the enzymatic responses of the individual cell types characterized. Female B6C3F1 mice were injected s.c. with five daily doses of 0.07-5.6 mu moles diethylstilbestrol (DES) or 17-beta estradiol. At 4 days posttreatment body and organ weights were recorded and bone marrow was collected for enumeration and assay of stem cell proliferative responses and enzyme analyses. Treatment with higher dose levels of either estrogenic chemical caused equivalent thymic atrophy, but DES resulted in greater liver and spleen hypertrophy than estradiol. Hexose monophosphate shunt dehydrogenase enzymes in unfractionated bone marrow cells were more sensitive to inhibition by lower estrogen doses than representative enzymes from glycolysis of the Kreb's Cycle, and on an equimolar basis were inhibited to a greater extent by DES than by estradiol. Enzyme analyses after density gradient cell separation indicated that 70-80% of the hexose monophosphate shunt enzyme activity in bone marrow from untreated mice occurred in the enriched band of cells containing predominantly granulocyte-macrophages. The majority of the enzyme inhibition induced by DES treatment could also be ascribed to this cellular population. Furthermore, it was shown that DES had a greater inhibitory effect on the proliferative capacity of the committed stem cells than on the multipotential stem cell population, and the main response was again expressed in the enriched band of cells containing predominantly granulocyte-macrophage precursors. Preliminary endocrine ablation experiments indicated estrogen inhibition of hexose monophosphate shunt enzyme activity was independent of the adrenal and the ovary, but was mediated through the thymus at lower estrogen concentrations.

Antioxidants attenuate anthralin-induced skin inflammation in BALB/c mice: role of specific proinflammatory cytokines.

Anthralin is the most common therapeutic agent among a small number of pro-oxidant, 9-anthrones effective in the topical treatment of psoriasis. However, the usefulness of this drug is diminished by toxic side effects, including skin irritation and inflammation. The activities of anthralin are believed to be mediated by the generation of reactive oxygen intermediates and anthrone radicals produced in the skin. In this study, the dermal inflammatory response to anthralin was determined using a mouse ear swelling test. Maximum ear swelling induced by anthralin coincided with the elevation of cytokine mRNA expression in the skin, including interleukin-6, granulocyte-macrophage colony-stimulating factor, macrophage inflammatory protein-2, and tumor necrosis factor alpha at 24 h post challenge. The role of free radical generation in ear swelling and cytokine modulation were examined by systemic administration of cell permeable and impermeable antioxidants before anthralin challenge. Superoxide dismutase and alpha-tocopherol acetate, but not the glutathione precursor N-acetyl cysteine, were effective inhibitors of anthralin-induced ear swelling and cytokine elevation. Maximum inflammatory cell infiltration occurred 72-96 h post anthralin challenge and was also reduced by antioxidants. These data suggest that oxidative stress, generated at the site of anthralin treatment, alters the expression of dermal chemokines and other cytokines resulting in the recruitment of inflammatory cells. Systemic antioxidant administration may provide opportunities for therapeutic intervention against anthralin-associated toxicities.

Cytokine induction in human epidermal keratinocytes exposed to contact irritants and its relation to chemical-induced inflammation in mouse skin.

In response to exogenous stimuli such as phorbol-12-myristate 13-acetate, ultraviolet B radiation, and lipopolysaccharide, human keratinocytes produce soluble mediators that are important in primary contact irritancy including cytokines that are associated with proinflammatory properties (interleukin-1 alpha [IL-1 alpha], tumor necrosis factor alpha), chemotaxis (IL-8), and growth activation (granulocyte/macrophage colony stimulating factor, IL-6, transforming growth factor alpha). We examined qualitative and quantitative changes in selected intracellular and secreted cytokines in human keratinocyte cultures in response to non-sensitizing contact irritants (croton oil, sodium lauryl sulfate, methyl salicylate, ethyl phenylpropiolate), sensitizing irritants (oxazolone, dinitrofluorobenzene), and ulcerative agents (phenol, benzalkonium chloride, chromium trioxide). The chemicals were also applied to mouse skin to assess whether the chemical-specific pattern of inflammation correlated with the in vitro production of keratinocyte-derived cytokines. Although all agents elicited neutrophils to the site of chemical application, time dependent and chemical-specific patterns of inflammation could be detected. Sodium lauryl sulfate, phenol, and croton oil induced increases in IL-8 production at non-cytotoxic concentrations in semi-confluent human keratinocyte cultures. Phenol and croton oil stimulated tumor necrosis factor alpha production, whereas croton oil was the only agent found to induce granulocyte/macrophage colony-stimulating factor production. Croton oil, phenol, benzalkonium chloride, and dinitrofluorobenzene induced the intracellular production of IL-1 alpha without a concomitant release into the medium. The release of cytokines occurred in parallel with a relative increase in cytokine-specific mRNA transcripts. Studies using neutralizing antibodies to tumor necrosis factor alpha and IL-1 alpha demonstrated that IL-8 induction by croton oil and phenol occurred directly rather than through autocrine circuits. These data suggest that a given pattern of cytokine production is chemical-specific and may predict the contribution of keratinocytes to skin inflammation.

Cytokine expression in hepatocytes: role of oxidant stress.

Inflammatory mediators, including cytokines and chemokines, are associated with the pathology of chronic liver disease. Interleukin-8 (IL-8) in humans and macrophage inflammatory protein-2 (MIP-2) in rodents, both members of the C-X-C family of chemokines, are particularly potent neutrophil attractants and have been implicated in chronic liver diseases. In the liver, cytokine secretion is usually associated with non-parenchymal cells, particularly Kupffer cells. In the present studies, chemokine gene expression and secretion were investigated in hepatocytes treated with various stimulators. Using human Hep G2 cells, it was demonstrated that, in contrast to lipopolysaccharides (LPS), both tumor necrosis factor-alpha (TNF-beta) and H2O2 are potent inducers of IL-8, presumably acting via protein kinase C (PKC)-dependent pathways. MIP-2 expression occurred in freshly isolated rat hepatocytes following treatment with TNF-alpha, LPS, and to a lesser degree, H2O2. Both IL-8 and MIP-2 secretion were inhibited, although to varying degrees, by such antioxidants as TMTU, DMSO, catalase, and N-acetylcysteine. Furthermore, in vitro TNF-alpha neutralization experiments and transfection of Hep G2 cells with an IL-8 construct confirmed that TNF-alpha and H2O2 directly stimulate IL-8 secretion. RT-PCR analyses indicated that chemokine secretion induced by these agents operates via increased gene expression. Furthermore, a variety of cytokine genes were found to be expressed by hepatocytes, including MCP-1, cytokine-induced neutrophil chemoattractant (CINC), and IL-6. Taken together, these studies indicate that hepatocytes respond to biologically relevant levels of common activators, including H2O2, to produce cytokines and chemokines that contribute to pathophysiologic and repair processes in the liver.

Interleukin-6 treatment augments cutaneous wound healing in immunosuppressed mice.

It has been postulated that the inflammatory response that occurs after cutaneous wounding is a prerequisite for healing and that inflammatory cytokines, such as interleukin-6 (IL-6) are involved in this process. We showed previously that IL-6-deficient mice display delayed wound healing, which could be reversed by administration of a murine IL-6 expression plasmid or recombinant murine IL-6 (rMuIL-6). In the present study, we observed that delayed cutaneous wound healing, which occurs as a result of glucocorticoid-induced immunosuppression, can also be reversed by rMuIL-6, as evidenced by epithelialization, granulation tissue formation, and wound closure. In vehicle control mice, rMuIL-6 did not augment healing but rather delayed the process. Immunochemical studies indicated that the expression of matrix metalloproteinase-10 (MMP-10) was increased in dexamethasone-treated mice and that rMuIL-6 treatment reduced its expression, indicating that IL-6 may influence dermal matrix formation and, specifically, collagen synthesis. These results demonstrate that IL-6 can restore abnormal wound repair that occurs in immunodeficiency and suggest its use as a potential therapy.

Trimethyltin increases interleukin (IL)-1 alpha, IL-6 and tumor necrosis factor alpha mRNA levels in rat hippocampus.

Within the central nervous system (CNS), cytokines are though to have active roles in pathophysiological changes seen in various neurological diseases and trauma. The present study was undertaken to examine the early response of pro-inflammatory cytokines following exposure to a specific neurotoxicant (trimethyltin; TMT). mRNA levels for interleukin (IL)-1 alpha, IL-1 beta, IL-6 and tumor necrosis factor (TNF) alpha were measured in the hippocampus of adult male Long-Evans hooded rats following an acute injection of trimethyltin hydroxide (8 mg TMT/kg body weight). At various times following exposure (6 h to 8 days), hippocampal tissues were excised and relative changes in cytokine mRNA levels were assessed by reverse transcription and polymerase chain reaction. IL-1 alpha, IL-6 and TNF alpha mRNA levels in the hippocampus increased within 6 h and remained elevated for 8 days. Quantitative analysis of mRNA transcripts revealed a two-fold increase in both IL-6 and TNF alpha within 6 h and a continued elevation of TNF alpha to 9-fold by 12 h. Within 96 h, glial fibrillary acidic protein (GFAP) mRNA levels were elevated in the hippocampus. Histological examination showed sparse individual neuronal necrosis at this time in both the pyramidal and granule cell regions with no increase in astrocyte GFAP immunoreactivity. However, an early, 24 h, response of microglial cells was indicated by increased lectin binding. This morphological profile progressed over time to a profound neuronal loss in the CA3-4 granule cell layer and marked astrocyte hypertrophy. The onset of pro-inflammatory cytokine mRNA expression appears to be temporally associated with histological evidence of elevated microglia in the hippocampus. It is proposed that microglia and pro-inflammatory cytokines play a modulatory role in the early stages of TMT-induced neurotoxicity.

Comparative assessment of metabolic enzyme levels in macrophage populations of the F344 rat.

The immune system is a direct target for toxic insult by a number of drugs and other chemicals, many of which require activation to toxic metabolites by drug-metabolizing enzymes. We compared the induction of drug-metabolizing enzymes, including cytochrome P450 1A1 (CYP1A1) and aldehyde dehydrogenase (ALDH), which are differentially expressed in various macrophage populations following treatment of F344 rats with the inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Kupffer cells, alveolar macrophages and splenic macrophages from TCDD-treated animals expressed elevated levels of inducible CYP1A1 as compared to other macrophage subpopulations or cells from control rats. TCDD treatment also resulted in increased ethoxyresorufin-O-deethylase (EROD) activity and total cytochrome P450 content in tissue-derived macrophages. Immunoreactive protein and mRNA transcripts for CYP1A1 were not detectable in resident peritoneal macrophages or peripheral blood monocytes. Examination of aromatic hydrocarbon receptor (AhR) levels in macrophage populations suggests that the ability of TCDD to induce metabolic enzymes in specific cell types correlates well with AhR expression. In vivo activation of macrophages, using either Bacillus of Calmette and Guérin, Mycobacterium tuberculosis (BCG) or polyinosinic:polycytidylic acid (Poly I:C), caused no significant alteration in the levels of induction of CYP1A1. ALDH-3 induction was similar in all macrophage populations examined. These studies indicate that macrophages, particularly those from portals of entry, may be induced to produce increased levels of specific enzymes, and the induction is dependent upon their maturational stage rather than their activation state. The metabolism of xenobiotics to toxic intermediates by immune cells and its role in immunosuppression are discussed.

Modulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-mediated myelotoxicity by thyroid hormones.

Although binding by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to the Ah receptor is a prerequisite for toxicity, the events responsible for subsequent TCDD effects are essentially unknown. Several lines of evidence have indicated that thyroid hormones share common molecular properties with TCDD and can modulate its toxicity. In the present studies we employed suppression of murine bone marrow hematopoiesis by TCDD as an in vitro model to study the relationship between thyroid hormones and TCDD toxicity. Supraphysiological levels of thyroid hormone mimicked TCDD myelotoxicity, in that both were inhibited by a common antagonist, 1-NH2-3,7,8-trichlorodibenzo-p-dioxin. Furthermore, myelotoxicity by both TCDD and thyroid hormone segregated with the Ah locus in congenic mice. These data provide evidence of a relationship between TCDD and thyroid hormones in that hormonal activity may help regulate TCDD toxicity.

Chemical agents and the immune response.

Our desire to understand the potential adverse human health effects of environmental chemical exposure has coincided with an increased understanding of the immune system and an appreciation of its complex regulatory network. This has spawned a broad interest in the area of immunotoxicology within the scientific community as well as certain concerns in the public sector regarding chemical-induced hypersensitivity and immunosuppression. The incidence of alleged human sensitization to chemicals has increased, in part, due to the fact that chemical companies are moving to larger and/or different markets. It has been estimated that 35 million Americans suffer from allergic disease, of which 2-5% are from occupational exposure. Although there is not yet a clear understanding of dose-response relationships or disease predisposition, there are many well-defined examples (isocyanates, anhydrides) of chemical sensitizers in humans and experimental animals. Evidence that chemicals suppress immune responses in humans is considerably less well established, although there is a public perception that chemicals generally cause immunosuppression. This perception has been fueled by highly publicized legal cases and scientific controversies within the academic and industrial communities. As a consequence of these public and scientific concerns, many of the regulatory agencies are developing immunotoxicity testing guidelines. At the present, however, there are limitations on adequate human methodology and data that allow the extrapolation of animal data to assess human risk. The potential for human immunosuppression remains of concern, however, because of a large database generated from animal studies that demonstrates immunosuppression as well as reports of immunosuppression in humans inadvertently (e.g., halogenated aromatic hydrocarbons) or occupationally (asbestos, benzene) exposed to xenobiotics.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in fetal thymic and liver hematopoietic cells as indicators of exposure to developmental immunotoxicants.

Recent studies indicate that immune development in humans and other species may be altered after perinatal exposure to immunotoxic environmental contaminants. However, limited information is available regarding appropriate tests that may adequately detect developmental immunotoxic compounds. Experiments in which pregnant laboratory rodents were exposed to a variety of immunotoxic environmental agents indicate that fetal thymus and liver immune cells may be quantitatively and qualitatively altered by immunotoxicant exposure and, thus, may serve as sensitive markers of developmental immunotoxicant exposure. In particular, depression of fetal thymic cell counts appears to be a common event following gestational exposure to immunotoxicants that produce this response in adult animals. Total hematopoietic cell counts in fetal liver, however, may be a poor indicator of immunotoxicant exposure. Altered marker expression in both fetal thymus and liver appears to be a highly sensitive indicator of gestational immunotoxicant exposure. Together, these reports suggest that immune tests with high predictability for immunosuppression in adults may also be appropriate for the detection of developmental immunotoxic agents.

Autoimmunity and risk assessment.

Among the issues dealing with identifying potential adverse immunologic effects (i.e., suppression, hypersensitivity, or autoimmunity) associated with xenobiotic exposure, general agreement exists among the regulatory and pharmaceutical communities that predictive tests for autoimmunity are in most need of development in order to improve risk assessment. The estimation of risk (i.e., the probability of a deleterious effect resulting from exposure) involves both the qualitative evaluation of whether a hazard exists and the quantitative evaluation for determining an acceptable level of exposure in humans. Unless adequate human data are available, which is uncommon, this is based on animal studies. Although animal models exist to study autoimmune processes, these models do not readily lend themselves to interpretation in the risk assessment process due, for the most part, to the complexity of autoimmune disease(s), as they are multifactorial and exhibit genetic heterogeneity in humans. To improve the risk assessment process, researchers must develop and validate animal models that not only incorporate mechanistic information into the assessment process but also allow for consideration of potent genetic, physiologic, and environmental influences.

Effects of polybrominated biphenyls (PBB) on immune response in rodents.

Studies were performed to investigate the effects of FireMaster FF-1, a chemical fire retardant consisting of a mixture of polybrominated biphenyls (PBB), on immune functions in mice and rats. Animals received 22 daily treatments of 0.03, 0.3, 3.0, or 30 mg PBB/kg body weight in a period covering 30 days. PBB exposure severely depressed cell mediated immunity in both mice and rats at the higher dosage levels as indicated by depressed responsiveness of splenic lymphocytes to mitogenic stimulation by polyclonal T-cell activators. Additionally, humoral immunity was depressed in mice at the 30.0 ppm dosage level. Assays for humoral immune functions included antibody production, serum immunoglobulin levels, and mitogenic stimulation of splenic lymphocytes to a polyclonal B-cell activator. These studies indicate that PBB exposure can lead to suppression of both humoral and particularly cell-mediated immune responses.

Cell-mediated immunity and its application in toxicology.

A variety of in vivo and more recently in vitro assays have been described to assess cell mediated immunity (CMI). Two methods routinely employed in our laboratory to assess CMI following exposure to chemicals in rodents include delayed hypersensitivity and in vitro lymphoproliferation. Preliminary studies indicate that depressed delayed hypersensitivity responses, as performed by a radiometric assay, correlates with altered susceptibility to infectious agents and tumor cell challenge following exposure to immunotoxic chemicals. Furthermore, suppression of T-cell lymphoproliferative responses to at least 50% below control values correlated with depressed delayed hypersensitivity responses and altered host susceptibility. On the other hand, when suppression of T-cell lymphoproliferative responses are within 50% of control values, delayed hypersensitivity and host susceptibility parameters are not affected. Assuming adequate technical expertise and accurate data interpretation, CMI assays of these types can provide a valuable data base for toxicology studies and immunotoxicity assessment.

Methods and approaches for assessing immunotoxicity: an overview.

The goals of the National Toxicology Program as they relate to immunological evaluation in toxicity assessment are discussed. The advantages of immune function assays for defining cellular injury as subtoxic levels following exposure to general or immunocyte specific chemical toxicants are proposed. A comprehensive screening panel of immune function and host resistance assays is presented in the context of an NIEHS approach for immunotoxicity assessment and methods selection. A second panel for defining the mechanism underlying immunological injury was also described. Studies utilizing these methods and approaches are described in companion papers by our group.

Perturbations of the immune system by xenobiotics.

Classically, immunotoxicology has been defined as the study of adverse effect on the immune system associated with exposure to environmental chemicals, pharmacologic agents, and biologicals. Although a multitude of immune system defects may occur, these can be generally categorized as immunomodulation (immune suppression or potentiation), hypersensitivity (i.e., allergy), and autoimmunity. We present here a brief synopsis of the ontogeny of immunotoxicology as a discipline including methodology currently used in our laboratory, as well as in others, for investigating the immunomodulatory potential of chemicals at the cellular and biochemical level. Additionally, we summarize some studies related to the immunosuppressive effects of one particular compound, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Last we discuss potential future directions and challenges in the field of immunotoxicology.

Application of tumor, bacterial and parasite susceptibility assays to study immune alterations induced by environmental chemicals.

Model systems to study the effects of chemicals of environmental concern on bacterial and parasitic diseases as well as the immunosurveillance and destruction of transplantable tumor cells were described and evaluated. Studies were conducted in female B6C3F1 mice following adult or pre/postnatal exposure to several prototype chemicals. The prototype chemicals employed included the synthetic estrogen diethylstilbestrol (DES), the polycyclic aromatic hydrocarbon benzo(a)pyrene (B[a]P), and the carcinogenesis promoting agent 12-0-tetradecanoyl-phorbol-13-0-acetate (TPA). The host resistance models employed depend primarily on functional thymus-dependent immunity, although humoral immunity is suggested to have a role in the parasite model as well. These models include: subcutaneous challenge with a dose of PYB6 tumor cell causing a 10-20% incidence (TD(10-20)) of tumor; intravenous challenge with B16 melanoma cells; challenge with a dose of Listeria monocytogenes causing a 10-20% incidence of mortality (LD(10-20)); challenge with a dose of E. coli lipopolysaccharide endotoxin causing a 10-20% incidence of lethality (LD(10-20)); and challenge with larvae of Trichinella spiralis for parasite expulsion kinetic studies. Increased mortality was observed following Listeria monocytogenes challenge in DES-exposed mice. B(a)P and TPA exposure did not alter host resistance to this organism. The increased mortality observed following DES was associated with a significant increase in the number of viable Listeria in the spleens and livers at 4 days, a time when T-cell immunity is thought to be expressed, but bacterial counts were similar to control mice at day 1, a time when MPhi are thought to exert their greatest effect. These data suggest that the increased Listeria susceptibility found following DES exposure may result from a T-cell defect, although the intracellular killing capacity of DES-treated Mvarphi's has not been well examined. Tumor susceptibility studies following challenge with 5 x 10(3) viable syngeneic PYB6 tumor cells revealed that nontreated adult B6C3F1 mice resisted tumor formation, with only a 10-20% incidence of tumor formation. In contrast, mice exposed to DES or TPA as adults had a tumor frequency of from 70-100% following TPA and up to 90% following DES exposure. In all cases the tumors were progressive and resulted in death. B(a)P did not alter the frequency of tumor incidence from controls in this model. Preliminary data, using the B16 melanoma intravenous challenge model and (125)IUdR to quantitate tumor mass revealed this model was sensitive to non-specifically activated macrophage kill. DES treated mice with activated macrophages did not demonstrate increased tumor mass, while mice exposed to TPA or the potent immunosuppressive agent cyclophosphamide had a significantly increased tumor mass in their lungs. Expulsion of Trichinella spiralis adults from the gut also apparently required functional T-cells and possibly some element of humoral immunity. Mice exposed to DES and B(a)P exhibited increased numbers of adult worms in the gut at day 14. Sensitivity to gram-negative endotoxin (LPS) was apparently increased following exposure to DES or B(a)P. These data suggest that the detoxification of LPS is related to an intact Mvarphi population. The data presented here demonstrate the sensitivity of the host resistance assay panel proposed for detecting immune alteration. Alteration of T-cell function appeared to correlate with increased susceptibility to bacterial and tumor cell challenge.