REGULATION OF THE POLYMERIC IMMUNOGLOBULIN RECEPTOR

分泌型免疫球蛋白A是免疫防御的第一道防线，保护 胃肠道和呼吸道的粘膜对 摄入和吸入病原体。分泌型IgA在体内的转运 外液是由聚合物免疫球蛋白受体(Poly-Ig-bb Reptor，Poly-Ig-R)介导的。 Ig-R)表达于粘膜上皮细胞表面。因为它的关键作用 在粘膜免疫方面，拟议的实验将探索这种调节 多聚Ig-R在人结肠癌亚克隆中的表达 细胞系HT-29.74，当细胞分化时 在不含葡萄糖的培养基中培养。多聚免疫球蛋白受体在HT-29.4中的表达 细胞在分化和处理过程中显著增加 细胞因子，如干扰素-γ和肿瘤坏死因子-α。 提出了三个具体目标来确定分子机制，通过 肠道分化过程中调节哪种多聚Ig-R 上皮细胞和特定免疫调节剂的作用。第一, 免疫调节剂干扰素-γ与肿瘤坏死的关系 凝血因子-α对多聚免疫球蛋白受体mRNA多聚免疫球蛋白受体蛋白稳态水平的影响 将确定HT-29.74细胞的特定分化阶段。 接下来，转录和转录后的贡献 将通过测量多聚Ig-R基因的体外比率来评估调节 Poly-Ig-R mRNA的转录和稳定性。最后，具体的顺位- Poly-Ig-R基因中介导其转录的作用DNA元件 调控将通过1)构建嵌合质粒来识别，在其中 Poly-Ig-R基因近端5‘侧翼区的片段有 被插入到报告基因的上游；2)将这些载体 对HT-29.74细胞的影响；以及3)测定肠细胞对 免疫调节剂对转录的影响及辨证论治 记者基因。拟议的实验提供了潜在的 识别控制分化的新调控机制-- Poly-Ig-R的特异性和细胞因子诱导表达此外， 拟议的研究有可能增加我们对 细胞因子一般调节免疫的分子机制 回应。加深对免疫调节机制的理解 肠道反应，包括干扰素-γ和肿瘤的影响 坏死因子-α，可能提供新的见解，可能导致更好的 粘膜表面传染病的防治， 包括艾滋病。

Secretory immunoglobulin A is the first line of immune defense, protecting the mucous membranes of the gastrointestinal and respiratory tracts against ingested and inhaled pathogens. The transport of secretory IgA into external fluids is mediated by the polymeric immunoglobulin receptor (poly- Ig-R) on the surface of mucosal epithelial cells. Because of its key role in mucosal immunity, the proposed experiments will explore the regulation of poly-Ig-R expression in a subclone of the human HT-29 colon carcinoma cell-line, HT-29.74, which undergoes enterocytic differentiation when cultured in medium devoid of glucose. Expression of poly-Ig-R by HT-29.4 cells is increased dramatically during differentiation and by treatment with cytokines such as interferon-gamma and tumor necrosis factor-alpha. Three specific aims are proposed to determine the molecular mechanisms by which poly-Ig-R is regulated during differentiation of intestinal epithelial cells and by the action of specific immune modulators. First, the effects of the immune modulators interferon-gamma and tumor necrosis factor-alpha on steady-state levels of poly-Ig-R mRNA poly-Ig-R protein at specific stages of differentiation of HT-29.74 cells will be determined. Next, the contribution of transcriptional and post-transcriptional regulation will be assessed by measuring in vitro rates of poly-Ig-R gene transcription and stability of poly-Ig-R mRNA. Finally, specific cis- acting DNA elements in the poly-Ig-R gene which mediate its transcriptional regulation will be identified by 1) constructing chimeric plasmids in which fragments of the proximal 5'-flanking region of the poly-Ig-R gene have been inserted upstream of a reporter gene; 2) transfecting these plasmids into HT-29.74 cells; and 3) determining the effects of enterocytic differentiation and treatment with immune modulators on transcription of the reporter gene. The proposed experiments offer the potential for identifying novel regulatory mechanisms which control the differentiation- specific and cytokine-induced expression of poly-Ig-R. In addition, the proposed studies have the potential to add to our understanding of the molecular mechanisms by which cytokines in general regulate immune responses. Increased understanding of mechanisms regulating immune responses in the gut, including the effects of interferon-gamma and tumor necrosis factor-alpha, may offer new insights that could lead to better prevention and treatment of infectious diseases of mucosal surfaces, including AIDS.