AHR SIGNALING PATHWAY AND B CELL INHIBITION BY TCDD

这项研究提案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，抑制免疫球蛋白(Ig)的分泌。这种抑制是由芳烃受体(AhR)介导的，该受体通过直接与Ig 3‘PIE重链增强剂(3’PIE增强剂)中的DRE位点结合来诱导不完全的Ig重链类开关。为了验证这一假设，使用小鼠双细胞系模型系统的分子和细胞方法将用于解决以下特定目标。在特定的目的1中，将AhR导入AhR缺陷的B细胞系将确定AhR是否是TCDD诱导的B细胞功能抑制所必需的。为了确定这种抑制是否是转录介导的，将在特定目的#2中检测AhR表达对TCDD诱导的蛋白质与二恶英反应增强子(DRE)和AKB基序结合的影响，这两个基序都位于3‘α增强子内。特定目的#3将评估TCDD对Ig重链类开关的影响，以及这种作用的AhR依赖性。这项研究的结果将促进目前对TCDD这种强大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.