Roles for the Aryl Hydrocarbon Receptor in the Immune Response to Toxoplasma Gondii

One of the major challenges faced by the immune system involves mounting an inflammatory response to control pathogen growth while limiting immune-mediated damage to the host. In order to achieve this balance, responding immune cells need to detect signals from the environment and react appropriately by promoting or attenuating inflammation. Cells of the immune system employ an array of sensors to respond to environmental cues, such as nuclear hormone receptors, cytokine receptors, and Toll-like receptors. The aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, provides immune cells with an additional means of detecting and responding to environmental signals to promote immunity. The work presented in this thesis examines the effects of AHR signaling during infection with the protozoan parasite Toxoplasma gondii, a medically significant pathogen that naturally infects mice. A variety of AHR ligands are produced by the host and the parasite during toxoplasmosis, which raised the question of whether AHR activity influences the immune response in this setting. Chapter 2 of this thesis describes a role for the AHR in promoting natural killer cell production of IL-10 in vitro and in vivo following infection. NK cells basally expressed the AHR and IL-12 stimulation increased AHR levels in these cells. Inhibition of the AHR led to impaired NK cell IL-10 production in vitro, and NK cells isolated from T. gondii-infected Ahr-/- mice had defective expression of IL-10. Chapter 3 demonstrates context-dependent roles for the AHR during oral and chronic toxoplasmosis. Orally infected Ahr-/- animals exhibited more severe weight loss and increased intestinal tissue pathology compared to wild-type mice, which was associated with CD4+ T cell hyperactivation. Chronically infected Ahr-/- mice developed elevated parasite burdens, but the CD4+ T cell responses in these animals were comparable to those in wild-type animals. Collectively these studies indicate that the AHR has multiple context dependent roles in the immune response to T. gondii

Relationship between Mental Health Symptoms and Reactive and Proactive Aggression Among Females in Residential Juvenile Justice Facilities

The female juvenile justice population has been traditionally overlooked in research, though it is the fastest-growing segment of the justice system. Intervention development should focus on this population, which is particularly high in both mental health symptom prevalence and levels and rates of aggression. This study examined the relationship between mental health symptoms (internalizing and externalizing) and aggression (reactive and proactive) among girls in residential juvenile justice facilities, and proposed mediators of this relationship (outcome expectations, hostile attribution bias, and anger). Multiple regression analyses indicated that symptoms of generalized anxiety disorder were associated with reactive aggression and with proactive aggression when controlling for symptoms of major depressive disorder, conduct disorder, oppositional defiant disorder, and attention-deficit/hyperactivity disorder. Parallel mediation analyses revealed that anger significantly mediated the relationships between the predictor variables of internalizing symptoms, generalized anxiety disorder, and externalizing symptoms and the outcome variables of reactive and proactive aggression, while outcome expectations and hostile attribution bias did not. Implications for future intervention development and research and limitations are discussed.M.S., Psychology -- Drexel University, 201

Risk Assessment for Future Offending: The Value and Limits of Expert Evidence at Sentencing

The question of a criminal defendant’s risk for future offending may be of interest to courts in a variety of contexts. Courts may request or consider information from forensic mental health professionals regarding risk assessment, which is the formal appraisal of the probability that an offender will reoffend or commit particular acts of violence in the future.1 Risk assessment is relevant in criminal contexts such as capital sentencing, criminal responsibility, and commitment of sexually violent predators; it also arises in civil contexts including civil commitment, workplace disability, child custody, and child protection.2 In some instances, risk assessment also may be done in cases involving risk of harm to identifiable third parties.3 Despite its growing use in the United States legal system in recent years, violence risk assessment has historically come under critical scrutiny in U.S. courts. Such concern about the practice of risk assessment and its evidentiary value is appropriate, considering the consequences that can be associated with a conclusion that an individual is high risk. Such consequences might include, inter alia, longer sentences or lost custody of a child.

HLA class I and II genotype of the NCI-60 cell lines

Sixty cancer cell lines have been extensively characterized and used by the National Cancer Institute's Developmental Therapeutics Program (NCI-60) since the early 90's as screening tools for anti-cancer drug development. An extensive database has been accumulated that could be used to select individual cells lines for specific experimental designs based on their global genetic and biological profile. However, information on the human leukocyte antigen (HLA) genotype of these cell lines is scant and mostly antiquated since it was derived from serological typing. We, therefore, re-typed the NCI-60 panel of cell lines by high-resolution sequence-based typing. This information may be used to: 1) identify and verify the identity of the same cell lines at various institutions; 2) check for possible contaminant cell lines in culture; 3) adopt individual cell lines for experiments in which knowledge of HLA molecule expression is relevant. Since genome-based typing does not guarantee actual surface protein expression, further characterization of relevant cell lines should be entertained to verify surface expression in experiments requiring correct antigen presentation

Parasite fate and involvement of infected cells in the induction of CD4+ and CD8+ T cell responses to Toxoplasma gondii

During infection with the intracellular parasite Toxoplasma gondii, the presentation of parasite-derived antigens to CD4+ and CD8+ T cells is essential for long-term resistance to this pathogen. Fundamental questions remain regarding the roles of phagocytosis and active invasion in the events that lead to the processing and presentation of parasite antigens. To understand the most proximal events in this process, an attenuated non-replicating strain of T. gondii (the cpsII strain) was combined with a cytometry-based approach to distinguish active invasion from phagocytic uptake. In vivo studies revealed that T. gondii disproportionately infected dendritic cells and macrophages, and that infected dendritic cells and macrophages displayed an activated phenotype characterized by enhanced levels of CD86 compared to cells that had phagocytosed the parasite, thus suggesting a role for these cells in priming naïve T cells. Indeed, dendritic cells were required for optimal CD4+ and CD8+ T cell responses, and the phagocytosis of heat-killed or invasion-blocked parasites was not sufficient to induce T cell responses. Rather, the selective transfer of cpsII-infected dendritic cells or macrophages (but not those that had phagocytosed the parasite) to naïve mice potently induced CD4+ and CD8+ T cell responses, and conferred protection against challenge with virulent T. gondii. Collectively, these results point toward a critical role for actively infected host cells in initiating T. gondii-specific CD4+ and CD8+ T cell responses

Risk Assessment for Future Offending: The Value and Limits of Expert Evidence at Sentencing

The question of a criminal defendant’s risk for future offending may be of interest to courts in a variety of contexts. Courts may request or consider information from forensic mental health professionals regarding risk assessment, which is the formal appraisal of the probability that an offender will reoffend or commit particular acts of violence in the future.1 Risk assessment is relevant in criminal contexts such as capital sentencing, criminal responsibility, and commitment of sexually violent predators; it also arises in civil contexts including civil commitment, workplace disability, child custody, and child protection.2 In some instances, risk assessment also may be done in cases involving risk of harm to identifiable third parties.3 Despite its growing use in the United States legal system in recent years, violence risk assessment has historically come under critical scrutiny in U.S. courts. Such concern about the practice of risk assessment and its evidentiary value is appropriate, considering the consequences that can be associated with a conclusion that an individual is high risk. Such consequences might include, inter alia, longer sentences or lost custody of a child.

ENERGY PARTITION OF A CORE MELT ACCIDENT IN A NUCLEAR POWER REACTOR (STEAM EXPLOSION, STRUCTURAL ANALYSIS)

A broad data base was established on the energetics of single-phase and two-phase discharge into a liquid pool. The experimental setup using simulant fluids was a 1/7 scale model of the core-and-vessel configuration of a loop-type liquid metal fast breeder reactor. The condensation-driven entrainment of the pool liquid into the expanding bubble was significant. The impact pressure on the top of the containment vessel dropped significantly because of heat transfer caused by the mixing of gas and liquid resulting from the Taylor instabilities formed at the pool-cover gas interface. The discharge of the steam-water mixture into the Freon-11 pool was energetic and resulted in high impact pressures. A parametric analysis was conducted for the thermal to mechanical energy conversion of a steam explosion accident in a pressurized water reactor. This study provides the groundwork for energy partition by providing the ideal explosion energy for a broad range of initial conditions. The structural analysis of the lower plenum of the reactor pressure vessel was conducted with the finite element computer code STRAW (A Nonlinear Fluid-Structural and Thermomechanical Finite Element Program), which was coupled with fluid modeling in order to account for the rapid pressure drop during expansion. During the very early stage of expansion, a significant amount of energy was transferred from the explosion mixture to the vessel wall and to the water which did not participate in the explosion. A detailed analysis of the expansion of the explosion mixture was conducted for eleven representative cases covering a broad range of explosion energy. The expansion analysis accounted for possible mechanisms of energy release. It was found that the explosion energy was 1/7 of that calculated under ideal conditions. A calculation of the slug impact on the upper core structural plate was conducted using STRAW. Approximately 35% of the kinetic energy of the slug, that initially was directed upward, was redirected along the radial direction and was dissipated into the UCSP and the core barrel by means of strain energy

Reduced Pathology following Infection with Transgenic Leishmania major Expressing Murine CD40 Ligand▿

Leishmanization is the inoculation of live Leishmania into the host to vaccinate against subsequent infections. This approach has been largely discontinued due to safety concerns. We have previously shown that combining CD40 ligand (CD40L) with Leishmania antigen preferentially induces a type 1 immune response and provides some protection to vaccinated mice (G. Chen, P. A. Darrah, and D. M. Mosser, Infect. Immun. 69:3255-3263, 2001). In the present study, we developed transgenic L. major organisms which express and secrete the extracellular portion of CD40L (L. major CD40LE). We hypothesized that these organisms would be less virulent but more immunogenic than wild-type organisms and therefore be more effective at leishmanization. Transgenic parasites expressing CD40L mRNA and protein were developed. BALB/c mice infected with these parasites developed significantly smaller lesions containing fewer parasites than animals infected with wild-type organisms. Infection of resistant C57BL/6 mice with low doses of transgenic parasites induced a significant amount of protection against subsequent high-dose infection with wild-type organisms. These results demonstrate that transgenic organisms expressing CD40L are less virulent than wild-type organisms while retaining full immunogenicity

Increased T cell responses to <i>Toxoplasma</i> antigen and crude commensal antigen in <i>Ahr</i>^<i>-/-</i> mice following infection.

<p>Wild type or <i>Ahr</i>^<i>-/-</i> mice were orally infected with 100 <i>T</i>. <i>gondii</i> cysts for 7 days. <b>(A, B)</b> Splenocytes were stimulated with the indicated antigen preparations for 5 hours and then incubated overnight with brefeldin A. The cells were stained to assay IFN-γ expression by CD4⁺ T cells. The graph shows pooled data from 3 independent experiments. <b>(C)</b> Parasite burdens in the terminal ileum were assayed by RT-PCR. Results are pooled from 2 separate experiments.</p