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Ahr-Mediated Transcriptional Regulation Of The Human Immunoglobulin Hs1.2 Enhancer, Sydney White

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The 3'IGHRR is thought to be responsible for the transcription of the immunoglobulin heavy chain (IGH) gene locus, which is essential for the production of antibodies. The human 3’IGHRR, which is duplicated in humans, contains the hs3, hs4, and hs1.2 enhancers. Additionally, the hs1.2 enhancer is polymorphic in humans and consists of a 53 bp invariant sequence that can be repeated one to four times. Previous experiments in a mouse and human B-cell line model have shown that the high affinity AhR ligand and environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can induce hs1.2 enhancer activity in an AhR-dependent manner. The AhR is …

Genomic Vs. Non-Genomic Role Of The Ahr In Human Immunoglobulin Expression, Nasser Alhamdan

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The immunoglobulin heavy chain gene (Igh) in various animal models is regulated by numerous regulatory elements including the 3’Igh regulatory region (3’IghRR). Several transcription factors are involved in modulating the 3’IghRR including the aryl hydrocarbon receptor (AhR). The AhR is a ligand-activated transcription factor that mediates the transcription of genes involved in the metabolism of environmental toxicants such as TCDD. TCDD binds AhR and regulates immunoglobulin (Ig) expression in B cells. This modulation appears to be directly mediated by binding of the AhR to dioxin response elements (DRE) within the 3’IghRR. In human B cells, IgG secretion inhibited by TCDD …

Genomic Vs. Non-Genomic Role Of The Ahr In Human Immunoglobulin Expression, Nasser Alhamdan

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The immunoglobulin heavy chain gene (Igh) in various animal models is regulated by numerous regulatory elements including the 3'Igh regulatory region (3'IghRR). Several transcription factors are involved in modulating the 3'R including the aryl hydrocarbon receptor (AhR). The AhR is a ligand-activated transcription factor that mediates the transcription of genes involved in the metabolism of environmental toxicants such as TCDD. TCDD binds AhR and regulates immunoglobulin (Ig) expression in B cells. This modulation appears to be directly mediated by binding of the AhR to dioxin response elements (DRE) within the 3'IghRR. In human B cells, IgG secretion inhibited by TCDD …

Determining The Role Of The Ahr In Immunoglobulin Expression And Class Switch Recombination, Bassam Fawaz Kashgari

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The aryl hydrocarbon receptor (AhR) is a ligand-activated cytosolic transcription factor that regulates xenobiotic-metabolizing enzymes. It mediates the toxicity of various environmental chemicals such as 2,3,7,8-tetracholorodibenzo-p-dioxin (TCDD). TCDD inhibits the differentiation of B cells into antibody-secreting cells and inhibits immunoglobulin (Ig) expression in various animal models. We have previously determined that TCDD-induced inhibition of the mouse Ig heavy chain gene (mo-Igh) is AhR-dependent. This inhibition may be mediated by binding of the AhR to dioxin response elements (DREs) within the 3'Igh regulatory region (3'IghRR) and inhibition of 3'IghRR activity, a significant transcriptional regulator of Ig expression. However, there are structural …

Elucidating The Effects Of Tcdd On The Polymorphic Human Hs1,2 Enhancer, Abdullah Freiwan

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2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent environmental toxin known to inhibit immunoglobulin (Ig) gene expression in various animal studies. We have identified the mouse 3'Ig heavy chain regulatory region (3'IgH RR) as a sensitive transcriptional target of TCDD, which may mediate the inhibitory effect of TCDD on Ig expression. Interestingly, the human hs1,2 enhancer is polymorphic and has been associated with a number of autoimmune diseases.

Suggesting a species difference, TCDD inhibited mouse hs1,2 enhancer activation and activated basal human hs1,2 (hs-hs1,2) enhancer activity in the mouse B-cell line. The objective of this study was to elucidate the effects of TCDD …

The Aryl Hydrocarbon Receptor Regulates An Essential Transcriptional Element In The Immunoglobulin Heavy Chain Gene, Michael J. Wourms

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2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a ubiquitous environmental contaminant that inhibits immunoglobulin (Ig) expression and Ig heavy (IgH) chain gene transcription. Transcription of the IgH gene involves several regulatory elements including the 3'lgh regulatory region (3'lghRR) which is composed of four enhancers (hs3A, hs1,2, hs4, and hs3B). Dioxin responsive elements (DRE) in the hs4 and hs1,2 enhancers of the 3lghRR that bind the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that regulates dioxin sensitive genes suggest that the 3'lghRR may be a transcriptional target of TCDD. The current study utilized an IgA secreting mouse …

Elucidating Transcription Factor Regulation By Tcdd Within The Hs1,2 Enhancer, Sharon D. Ochs

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Immunoglobulin heavy chain (IgH) expression and Ig secretion is inhibited by the environmental contaminant 2,3,7,8-tetrachlorodibenzo-ρ-dioxin (TCDD). Within the IgH gene, the 3' IgH regulatory region (3'IgH RR) has been identified as a transcriptional target of TCDD. The 3'IgH RR, which in part regulates transcription of the IgH gene, is composed of four enhancers in the mouse: hs3a; hs1,2; h3b; hs4 and three enhancers in the human: hs3a; hs1,2; hs4. In humans the hs1,2 enhancer has an invariant sequence (IS) containing a DRE, NF-κB, NF1 and AP-1 binding site. Also, the enhancer has an AP1.ETS and Oct …

2,3,7,8-Tetrachlordibenzo-P-Dioxin Mediated Immune Suppression Through Interactions At The 3'Immunoglobulin Heavy Chain Regulatory Region Enhancers, David Harold Ellis

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2,3,7,8-Tetrachlordibenzo-p-dioxin (TCDD) is a potent toxin which inhibits the antibody response of B cells. The 3'IgHRR which is involved in transcriptional regulation of the heavy-chain polypeptide of antibodies is inhibited by TCDD. The hs1,2 enhancer region, isolated from the 3'IgHRR, is also inhibited while the isolated hs4 is activated by TCDD. This project sought to determine if that dichotomy in effects results from interactions at enhancer-specific binding sites for AhR, thought to mediate transcriptional effects of TCDD, and NFκB, a transcription factor involved in B cell activation. Here, I report a difference in the effect of TCDD on transcriptional activity …

The Im-9 Cell Line: A Model For Evaluating Tcdd-Induced Modulation Of The Polymorphic Human Hs1,2 Enhancer Within The 3' Immunoglobulin Heavy Chain Regulatory Region, Ruth C. Chambers-Turner

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2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a disrupter, of B-cell differentiation, induces binding of the aryl hydrocarbon receptor (AhR) nuclear complex to dioxin responsive elements (DRE) within the mouse immunoglobulin heavy chain regulatory region (3'IgHRR), and produces a marked inhibition of 3'IgHRR activation, IgH expression, and antibody secretion in a well-characterized mouse B-cell line (CH12.LX). The mouse 3'IgHRR consists of at least four enhancers (hs3a; hs1,2; hs3b; hs4), and is highly homologous with the three enhancers (hs3; hs1,2; hs4) of the human 3'IgHRR. A polymorphism of the human hs1,2 enhancer (resulting in varying numbers of tandem repeats containing a DRE and κB site) has …

Tcdd-Induced Modulation Of The Hs1,2 Enhancer Within The 3'Immunoglobulin Heavy Chain Regulatory Region, Tharu M. Fernando

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2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a potent environmental toxin that inhibits immunoglobulin (Ig) gene expression in mice. Transcriptional regulation of the Ig heavy chain (IgH) involves the 3'IgH regulatory region (3'IgH RR). The murine 3'IgH RR consists of four enhancers (hs3A, hs1,2, hs3B, and hs4), which are homologous to the human 3'IgH RR enhancers (hs3, hs1,2, and hs4). In humans, a polymorphism of the hs1,2 enhancer, resulting in a varying number of tandem repeats of a 53 bp sequence, has been correlated with autoimmune diseases like IgA nephropathy and Celiac disease. The repeated sequence contains a kB and DRE binding site. Previous …

Nmr Analyses Show Tcdd Elicits Differences In Hepatic Metabolism In Female C57bl/6 Mice And Sprague-Dawley Rats, Meghan Katherine Makley

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TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) elicits tissue-, sex-, and species-specific effects. This study compares the hepatic response to an oral dose of TCDD in immature ovariectomized (i.o.) C57BL/6 mice (30 µg/kg) and i.o. Sprague-Dawley rats (10 µg/kg), at 72, 120, and 168 h post-dose. Hepatic lipid extracts were analyzed by ¹³C and ³¹P NMR, and aqueous extracts by ¹H and ³¹P NMR.

Consistent with increased lipid content in mice (p≤0.05), TCDD induced increases in hepatic triacylglycerides (TAG), cholesterol, and fatty acids. Principal component analysis of ¹³C spectra show treatment groups separate in mice, but not rats. …

Modulation Of The 3'Igh Regulatory Region (3'Igh Rr), A Prospective In Vitro Screening Tool For Identifying Potential Immunotoxicants, Rebecca Anne Henseler

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The immune system is critical to human survival. However, assessing alterations of immune function by potential immunotoxicants is complicated by the diffuse nature of the immune system, which is composed of various effector cells each with differing effector functions. Current immunotoxicity testing is limited to animal studies. We have developed a model, which may provide an in vitro alternative to animal studies in identifying immunotoxicants that specifically target B cell function (i.e., alteration of immunoglobulin (Ig) or expression and antibody secretion). This model consists of a well-characterized B cell line, CH12.LX, which appears to appropriately model primary B cell function. …

Immunological And Developmental Effects Of Polybrominated Diphenyl Ethers (Pbdes) And 2,3,7,8-Tetrachloro-P-Dioxin (Tcdd) In Birds, Randy T. Stetzer

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This thesis contains two separate and distinct research projects with a common overall theme - the study of immunotoxicity associated with the developmental exposure of young birds to halogenated chemicals posing environmental concern. These chemicals share many chemical characteristics, including environmental ubiquity and longevity, one has been studied extensively since the 1970s, and one is a relatively new environmental contaminant with few studies pertaining to toxicological affects on humans or wildlife. Specific summaries of each study begin each project chapter. The first study was entitled Developmental and Immunological Effects of a Commercial Mixture of PBDE Flame Retardants in Chicken Embryos. …