Monocrotaline (MCT) is a member of a class of naturally occurring phytotoxins known as pyrrolizidine alkaloids (PAs). Exposure to PAs can result in liver and cardiopulmonary lesions as well as lymphoid organ atrophy. In the present study C57BI/6 (B6) mice received MCT (0-150 mg/kg/day, po) for 14 days. Overt toxicity was minimal and observed only at highly immunosuppressive doses. Following MCT exposure, significant dose-dependent suppressions were observed in the following immune responses: numbers of antibody producing cells, cytotoxic T- lymphocyte activity, and NK cell cytotoxicity. The antibody responses to the T cell-dependent antigen, SRBC, and the T cell-independent (TI) antigens, DNP-Ficoll and TNP-LPS, were decreased with identical dose response curves. This, along with data showing MCT decreased blastogenesis of B cells more than T cells at the lowest dose level, and that high doses induced significant decreases in the total number of B cells only, suggest that the B cell may be more sensitive than T cells, NK cells , or macrophages. The liver and lung toxicity of MCT is believed to be mediated through its metabolism by mixed function oxidase (MFO) enzymes to reactive pyrroles (monocrotaline pyrrole, MCTP; and dihydropyrrolizine, DHP). Accordingly, it was our hypothesis that the immunotoxicity could be modulated by altering MFO activity. To test this, mice were given a single dose of MCT (100 or 200 mg/kg, po) after MFO induction with phenobarbital; in other experiments mice received the MFO inhibitor chloramphenicol immediately before and 3 hrs after a single exposure to MCT (300 mg/kg, po). However, neither MFO induction nor inhibition significantly altered the immunosuppressive potency of MCT. The antibody and blastogenic responses of splenic lymphocytes directly exposed to MCT (1-3 mM) or MCTP (1-8 μM) in culture were inhibited in a concentration-dependent manner, indicating that both parent and metabolite were immunotoxic. However, the inability to alter the in vivo immunotoxicity by altering MFO activity questions the role this metabolite may play in vivo. In conclusion, the immune system in B6 mice is a sensitive target of MCT toxicity. Inhibition of blastogenesis appears to be one mechanism of MCT-induced immunosuppression. In contrast to other toxic effects of MCT, our results suggest that the parent compound itself plays a significant role in the immunotoxicity. / Graduation date: 1992

Acetaldehyde, the first metabolite of ethanol, has been implicated in the pathogenesis of alcoholic liver disease. In order to investigate a possible immunologic mechanism whereby acetaldehyde might exert its toxic effect acetaldehyde protein conjuates were prepared and characterized. This study demonstrates that acetaldehyde conjugated albumin can be an immunogen, can form a more negatively charged, more acidic, heterogeneous conjugate than albumin and can elicitate a specific rabbit antibody. ELISA can be used to assay antibodies produced in response to acetaldehyde albumin conjugates suggesting that chronic alcohol ingestion can lead the generation of antibodies against acetaldehyde conjugated human serum albumin. The significance of this study is that it possibly can provide a method to investigate the mechanism responsible for the sequelae of alcoholism.

T cell-dependent immune responses are highly sensitive to suppression by exposure to the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), yet direct effects of TCDD on T cells have been difficult to demonstrate. Because the activation of naive T cells is initiated by dendritic cells (DC), the studies presented in this dissertation were designed to test the hypothesis that TCDD affects these antigen-presenting cells in a manner which ultimately results in suppressed T cell activation. The expression of numerous cell surface proteins known to be important in signaling T cells to proliferate and differentiate was evaluated on splenic DC from C57B1/6 and Balb/c mice. The production of IL-12 and the ability of DC to activate allogeneic and antigen-specific T cells were also tested. Contrary to expectation, exposure to TCDD resulted in enhanced expression of several accessory molecules including B7-2, CD40, ICAM-1, CD24 and the major histocompatibility complex (MHCII). In contrast, expression of LFA-1 was significantly decreased on DC from TCDD-treated mice. These effects were dose-dependent, persisted for at least 14 days, and did not occur in aryl hydrocarbon receptor (AhR)-deficient mice. Interestingly, TCDD treatment also decreased the numbers of DC recovered from the spleen by day 7 following exposure in C57B1/6 mice and by day 3 in Balb/c animals. When T cells were cultured with DC from TCDD-treated mice, the proliferative response of the T cells and the production of IL-2, IL-4, and IFN-�� was not suppressed but instead tended to be increased. DC production of IL-12 was also enhanced. Furthermore, TCDD did not interfere with the ability of DC to internalize latex beads or to activate antigen-specific T cells, suggesting that uptake and processing of antigen by DC is not impaired by TCDD. AhR message was detected in splenic DC and AhR protein was found in two DC cell lines, indicating that DC may be directly affected by TCDD. Taken together, these results suggest that TCDD provides an activation stimulus to DC and may lead to their premature deletion. The relationship between these effects and TCDD-induced immune suppression remains to be determined. / Graduation date: 2001

Graduation date: 1998

Graduation date: 1997

Some fish populations are able to adapt and thrive in contaminated habitats. Survival of populations depends on the ability of the organism to elicit resistance, either due to genetic adaptation or physiological acclimations. Brown Bullheads (Ameiurus nebulosus) are able to survive in very contaminated areas and their benthic and philopatric characteristics make them a model organism to study chronic exposure. This research assesses the immune function of brown bullhead collected at four pre-determined sites along the Detroit River, which are characterized by high or low concentrations of environmental toxicants. Clean and contaminated sediment used for contaminant exposure was collected by ponar at designated sites of the river. The bullheads were vaccinated with heat-killed V. anguillarum in order to induce an immune response, before the vaccinated bullheads were randomly divided into corresponding contaminant exposure tanks. Respiratory burst assays to assess innate oxygen radical production 24hrs post vaccination and sediment exposure identified an inhibition of neutrophil oxidative activity in adult 6 month cleared of contaminant bullheads collected from a clean (Peche Island) site exposed to contaminated sediment, and of F1 raised populations from a contaminated (Trenton Channel) site. Results also showed overall inhibition on contaminated sediment in both PI and TC recently captured fish. Enzyme linked immunosorbant assay (ELISA) to assess antibody production revealed no difference between those fish exposed to either sediment. Results did show a lower expression of total antibody in chronically contaminant exposed bullheads (acute adults). Real time PCR to assess immune gene expression was conducted using cloned Major Histocompatibility Class II Beta (MHIIB), Interleukin-8 (IL-8) and Interleukin-1 Beta (IL-1B) 24hr post vaccination and sediment exposure. No contaminant induced immunosuppression of MHIIB was observed, while a reduction in IL-8 and IL-1B in acute adults may signify a delayed response due to chronic sediment exposure or of a normal functioning delayed response in wild bullheads. Results of the present study indicate negative environmental impacts on the innate immune response, leading to physiological adaptations in the brown bullhead, which can be reversed upon removal of the contaminants.

Some fish populations are able to adapt and thrive in contaminated habitats. Survival of populations depends on the ability of the organism to elicit resistance, either due to genetic adaptation or physiological acclimations. Brown Bullheads (Ameiurus nebulosus) are able to survive in very contaminated areas and their benthic and philopatric characteristics make them a model organism to study chronic exposure. This research assesses the immune function of brown bullhead collected at four pre-determined sites along the Detroit River, which are characterized by high or low concentrations of environmental toxicants. Clean and contaminated sediment used for contaminant exposure was collected by ponar at designated sites of the river. The bullheads were vaccinated with heat-killed V. anguillarum in order to induce an immune response, before the vaccinated bullheads were randomly divided into corresponding contaminant exposure tanks. Respiratory burst assays to assess innate oxygen radical production 24hrs post vaccination and sediment exposure identified an inhibition of neutrophil oxidative activity in adult 6 month cleared of contaminant bullheads collected from a clean (Peche Island) site exposed to contaminated sediment, and of F1 raised populations from a contaminated (Trenton Channel) site. Results also showed overall inhibition on contaminated sediment in both PI and TC recently captured fish. Enzyme linked immunosorbant assay (ELISA) to assess antibody production revealed no difference between those fish exposed to either sediment. Results did show a lower expression of total antibody in chronically contaminant exposed bullheads (acute adults). Real time PCR to assess immune gene expression was conducted using cloned Major Histocompatibility Class II Beta (MHIIB), Interleukin-8 (IL-8) and Interleukin-1 Beta (IL-1B) 24hr post vaccination and sediment exposure. No contaminant induced immunosuppression of MHIIB was observed, while a reduction in IL-8 and IL-1B in acute adults may signify a delayed response due to chronic sediment exposure or of a normal functioning delayed response in wild bullheads. Results of the present study indicate negative environmental impacts on the innate immune response, leading to physiological adaptations in the brown bullhead, which can be reversed upon removal of the contaminants.

Thesis (M.S.)--University of North Texas, May, 2007. / Title from title page display. Includes bibliographical references.

The earthworms, Lubricus terrestris and Eisenia foetida, were used as non mammalian surrogate models to assess the immunotoxicpotential of xenobiotic to mammals. Assays were developed and optimized for detecting spreading activity and phagocytosis of rabbit red blood cell (RRBC), bacteria, and yeasts by macrophage-like coelomocytes of L. terrestris.

This research evaluated the potential of activation and attachment, as sequential companion biomarkers of phagocytosis by earthworm, Lumbricus terrestris, immunoactive coelomocytes for use in immunotoxicology. The potential was assessed by exposing earthworms to sublethal concentrations of CuSO4 and Arochlor 1254®, chemicals used as reference or standard immunotoxicants.