Antigen Specific T Cell Tolerance by Anti CD3 Antibodies

描述(申请人提供)：本项目的长期目标是 开发诱导外周T细胞耐受的方法，以提高其耐受性 人类移植物排斥反应和移植物抗宿主病的预防 骨髓移植。我们认为，通过了解这一机制， 在小鼠模型中抗CD3-epsilon抗体的免疫抑制，我们将 能够利用抗CD3-epsilon抗体实现耐受性 在人类身上。抗CD3-epsilon F(ab‘)2给出“死亡能力”信号 抗原激活的循环T细胞。T细胞死亡需要两种“能力” TCR或抗CD3 F(ab‘)2产生的“Die”信号和Fas-L的表达 既往抗原暴露，或FasL+细胞接近。在移植的小鼠中 用针对LD同种异体抗原的CD8+TCR转基因2C细胞和OT-I 无H_2d反应的细胞，用抗CD3-epsilon F(ab‘)2处理 选择性地消耗2C细胞，防止移植物抗宿主病的表现。因此， 抗CD3-epsilon抗体可通过耗竭诱导选择性免疫抑制 抗原激活的T细胞。抗CD3-epsilon F(ab‘)2延迟但不能阻止 皮肤移植的排斥反应，表明其疗效有限。活体内 抗CD3-epsilon F(ab‘)2对TCR复合体的调节可能限制治疗 由于激活诱导T细胞死亡，因此有效并排除克隆性缺失 需要信令超过TCR的临界门限才能足够 时间到了。我们已经产生了一种低亲和力的抗CD3-epsilon突变抗体 与野生型相比，在更大的浓度范围内激活T细胞死亡 抗CD3-epsilon抗体。我们将检验低亲和力的假设 抗CD3-epsilon抗体在诱导细胞耗竭方面更有效 体内激活的T细胞。由于低亲和力多肽可以诱导T细胞 没有细胞因子分泌的细胞凋亡，我们考虑了这样的假设 低亲和力抗CD3-epsilon单抗可能不能诱导细胞因子的分泌， 在体内可能更安全。我们提供了CD3和CD4的初步数据 共刺激提供了一个积极的信号，而不是死亡的信号 预激活的T细胞。利用低亲和力抗CD3-epsilon F(ab‘)2突变体 带有fyn-/-和lck-/-外周T细胞的抗体和突变小鼠品系， 我们建议检验“死亡的补偿”信号是 通过src酪氨酸激酶Fyn而不是Lck进行转导。具体目标 主要有：1)设计低亲和力CD3配体，改进免疫抑制作用 功效。2)选择低亲和力的CD3配体诱导细胞凋亡 抗原激活的T细胞，但无致病性。3)定义信号通路 它们激活T细胞的凋亡，以响应CD3的连接。

DESCRIPTION (PROVIDED BY APPLICANT): The long-term goal of this project is to develop methods for induction of peripheral T cell tolerance that could improve prevention of graft rejection and graft-versus-host disease (GVHD) after human marrow transplantation. We propose that by understanding the mechanisms of immunosuppression by anti-CD3-epsilon antibodies in murine models, we will be able to exploit the use of anti-CD3-epsilon antibodies for achieving tolerance in man. Anti-CD3-epsilon F(ab')2 confers a "competence to die" signal to antigen-activated, cycling T cells. T cell death requires both a "competence to die" signal from the TCR or anti-CD3 F(ab')2, and FasL expression induced by prior antigen exposure, or the proximity of FasL+ cells. In mice transplanted with CD8+ TCR transgenic 2C cells specific for the Ld alloantigen, and OT-I cells that are not H2d-reactive, treatment with anti-CD3-epsilon F(ab')2 selectively depleted 2C cells and prevented manifestations of GVHD. Thus, anti-CD3-epsilon antibodies can induce selective immunosuppression by depletion of antigen-activated T cells. Anti-CD3-epsilon F(ab')2 delay but do not prevent rejection of skin grafts, indicating that their efficacy is limited. In vivo modulation of the TCR complex by anti-CD3-epsilon F(ab')2 may limit treatment efficacy and preclude clonal deletion, since activation-induced T cell death requires signaling above a critical threshold of TCRs engaged for sufficient time. We have generated a low avidity anti-CD3-epsilon mutant antibody which activates T cell death over a broader range of concentrations than wild type anti-CD3-epsilon antibody. We will test the hypothesis that low avidity anti-CD3-epsilon antibodies are more efficient at inducing depletion of activated T cells in vivo. Since low avidity peptides can induce T cell apoptosis without cytokine secretion, we have considered the hypothesis that low avidity anti-CD3-epsilon mAb may be unable to induce cytokine secretion, and may be safer in vivo. We present preliminary data that the CD3 and CD4 costimulation provides a positive signal rather than a death signal to pre-activated T cells. By using low avidity anti-CD3-epsilon F(ab')2 mutant antibodies and mutant mouse strains with fyn-/- and lck-/- peripheral T cells, we propose to test the hypothesis that the "compentence to die" signal is transduced through the src tyrosine kinase Fyn rather than Lck. Specific aims are: 1) Design low avidity CD3 ligands with improved immunosuppressive efficacy. 2) Select for low avidity CD3 ligands which induce apoptosis of antigen-activated T cell but no pathogenicity. 3) Define signaling pathways which activate T cell apoptosis in response to CD3 ligation.