IN VIVO REGULATION OF IGE PRODUCTION

对环境空气中非致病性抗原（过敏原）的免疫反应加剧是哮喘发生的主要因素之一。气道中的过敏反应是由肥大细胞上IgE分子的抗原交联引发的，导致平滑肌收缩和炎症的活性介质的脱颗粒和释放。已有研究表明，过敏反应的重要决定因素之一是2型辅助T淋巴细胞（Th2）的刺激，Th2通过认知性过敏反应刺激2型辅助T淋巴细胞（Th2）， Th2通过认知性T/B相互作用和IL-4分泌介导B淋巴细胞向IgE产生的转换，并通过IL-5的分泌调节嗜酸性粒细胞的募集、分化和活化。这一应用主要集中在体内调节IgE的产生。通过同源重组，我们将流感血凝素特异性B杂杂瘤中重排的VDJ重链基因和重排的VJ轻链基因插入到小鼠基因组中。来自这些小鼠的B细胞维持控制体细胞超突变和同型转换的生理因素，但是，与正常细胞相反，抗原特异性细胞的命运可以很容易地遵循。这些小鼠将使我们能够评估促进同型转换为IgE的不同信号的相对重要性，从而确定可以阻止或下调IgE生成的方法。具体来说，我们将：1)确定有利于在体内产生抗原特异性IgE的条件；2)评估B细胞受体对其抗原的亲和力对免疫球蛋白类转换的重要性；3)确定表达与IgE抗体相同抗原特异性的非IgE抗体是否可以调节气道内的反应；4)确定T细胞是否参与了IgE反应的下调。我们相信，本实验将增强我们对抗原反应中IgE产生调控的认识，并将为特应性疾病的治疗开辟新的途径。

Exacerbated immune responses to environmental airborne non-pathogenic antigens (allergens) are one of the main factors for the development of asthma. Allergic reactions in the airways are triggered by antigen crosslinking of IgE molecules on mast cells, leading to degranulation and release of active mediators of smooth muscle constriction and inflammation. It has been shown that one of the essential determinant of allergic responses is the stimulation of T helper lymphocytes of the type 2 (Th2), which, through cognitive allergic responses is the stimulation of T helper lymphocytes of the type 2(Th2), which, through cognitive T/B interaction and IL-4 secretion mediate B lymphocyte switch to IgE production, and through the secretion of IL-5 regulate the recruitment, differentiation and activation of eosinophils. This application is focused on the in vivo regulation of IgE production. Using homologous recombination, we have inserted a rearranged VDJ heavy chain gene as well as a rearranged VJ light gene from an influenza hemagglutinin-specific B hybridoma into the genome of mice. B cells from these mice maintain the physiological elements controlling somatic hypermutation and isotype switching, but, contrary to normal cells, the fate of antigen-specific cells can be easily followed. These mice will enable us to assess the relative importance of the different signals which promote isotype switching to IgE, thus defining ways in which the generation of IgE could be prevented or down-regulated. Specifically, we will: 1) determine the conditions which favor the generation of antigen-specific IgE in vivo; 2) assess the importance of the affinity of the B cell receptor for its antigen on immunoglobulin class switch; 3) determine whether non-IgE antibodies expressing the same antigen- specificity of IgE antibodies can modulate the response in the airways, and 4) determine whether T cells are involved in the down-regulation of IgE responses. We believe that the proposed experiments will enhance our knowledge on the regulation of IgE production in response to antigen, and will open new avenues for therapy of atopic disease.