AHR SIGNALING PATHWAY AND B CELL INHIBITION BY TCDD

本研究计划的总体目标是检验以下假设：2，3，7，8-四氯二苯并对二恶英（TCDD）直接作用于B细胞以抑制免疫球蛋白（IG）分泌。这种抑制由芳香烃受体（AhR）介导，其通过直接结合IG 3' pie重链增强子（3' pie增强子）内的DRE位点诱导不完全的IG重链类别转换。为了检验这一假设，将利用使用鼠双细胞系模型系统的分子和细胞方法来解决以下具体目标。在具体目标#1中，将AhR转染到AhR缺陷型B细胞系中将确定AhR是否对于TCDD诱导的B细胞功能抑制是必需的。为了确定这种抑制是否是转录介导的，将在具体目标#2中检查AhR表达对TCDD诱导的蛋白质与二恶英应答增强子（DRE）和akB基序（均位于3 'α增强子内）结合的影响。具体目标#3将评价TCDD对IG重链类别转换的影响，沿着该影响的AhR依赖性。本研究的结果将促进目前对TCDD这种强而持久的环境污染物改变B细胞功能的机制的理解。

The overall goal of this research proposal is to test the following hypothesis: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) acts directly on B-cells to suppress immunoglobulin (Ig) secretion. This suppression is mediated by the aryl hydrocarbon receptor (AhR) which induces an incomplete Ig heavy chain class switch by directly binding DRE sites within the Ig 3' pie heavy chain enhancer (3' pie enhancer). To test this hypothesis, a molecular and cellular approach using a murine two cell line model system will be utilized in addressing the following specific aims. In specific aim # 1, transfection of the AhR into an AhR-deficient B-cell line will determine if the AhR is essential for TCDD-induced inhibition of B-cell function. To determine if this inhibition is transcriptionally mediated, the effect of AhR expression on TCDD-induced protein binding to the dioxin responsive enhancer (DRE) and akB motif, both located within the 3'alpha enhancer, will be examined in specific aim #2. Specific aim #3 will evaluate the effect of TCDD on Ig heavy chain class switch, along with the AhR-dependency for this effect. The results of this research will advance the current understandig of the mechanism by which TCDD, a potent and persistent environmental contaminant, alters B-cell function.