Antigen Specific T Cell Tolerance by Anti CD3 Antibodies

描述（由申请人提供）：本项目的长期目标是 开发诱导外周T细胞耐受的方法， 预防人类移植后的移植物排斥和移植物抗宿主病（GVHD） 骨髓移植我们建议，通过了解 在小鼠模型中通过抗CD3-CD4抗体的免疫抑制，我们将 能够利用抗CD3-CD4抗体实现耐受性 抗CD3-CDIF（ab '）2赋予人"死亡能力"信号， 抗原激活的循环T细胞。T细胞死亡需要“能力， 来自TCR或抗-CD3F（ab '）2的"死亡"信号，以及 先前的抗原暴露，或接近FasL+细胞。在小鼠移植 用对Ld同种异体抗原特异性的CD8 + TCR转基因2C细胞，和OT-I 非H2d反应性细胞，用抗CD3-CDIF（ab '）2处理 选择性地耗尽2C细胞并防止GVHD的表现。因此，在本发明中， 抗CD3-CD4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-CDIF（ab '）2延迟但不预防 皮肤移植排斥反应，表明其疗效有限。体内 抗CD3-CDIF（ab '）2对TCR复合物的调节可能限制治疗 因为活化诱导T细胞死亡 需要高于TCR临界阈值的信号， 时间我们已经产生了低亲合力抗CD3-CD4突变体抗体， 在比野生型更宽的浓度范围内激活T细胞死亡 抗CD3-CD4抗体。我们将检验低亲合力 抗-CD3-CD4抗体在诱导消耗 体内活化T细胞。由于低亲合力肽可以诱导T细胞 在没有细胞因子分泌的细胞凋亡中，我们考虑了这样的假设， 低亲合力抗-CD3-mAb可能不能诱导细胞因子分泌， 并且在体内可能更安全。我们目前的初步数据表明，CD3和CD4 共刺激提供了一个积极的信号，而不是死亡信号， 预活化的T细胞通过使用低亲合力抗CD3-CDIF（ab '）2突变体， 抗体和具有fyn-/-和lck-/-外周T细胞的突变小鼠品系， 我们建议检验"死亡能力"信号是 通过src酪氨酸激酶Fyn而不是Lck转导。具体目标 1）设计具有改善的免疫抑制作用的低亲合力CD3配体 功效2)选择低亲合力CD3配体，其诱导细胞凋亡， 抗原活化T细胞，但无致病性。3)定义信号通路 其响应于CD3连接而激活T细胞凋亡。

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.