Role of CD47 in xenograft rejection by macrophages

CD47 在巨噬细胞异种移植排斥中的作用

• 批准号: 7989143
• 负责人: YONG-GUANG YANG
• 金额: $ 31.88万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-12-01 至 2012-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7989143
• 关键词: Affect; Antibodies; Attenuated; Binding; CD47 gene; Cell Line; Cells; Chimeric Proteins; Chimerism; Clinical; Clinical Trials; Complement; Cytolysis; Data; Dendritic Cells; Dendritic cell activation; Development; Engraftment; Extracellular Domain; FUS-1 Protein; Failure; Family suidae; Future; Genetic; Goals; Hematopoietic; Human; Immune; Immune response; Immunosuppression; Immunosuppressive Agents; Investigation; Lead; Ligands; Mediating; Membrane; Modeling; Molecular; Mus; Natural Killer Cells; Organ; Organ Donor; Phagocytes; Phagocytosis; Play; Predisposition; Regimen; Regulatory T-Lymphocyte; Role; SHPS-1 protein; Signal Transduction; Solutions; Source; Species Specificity; Stem cells; T cell response; T-Lymphocyte; Testing; Transfusion; Transgenic Mice; Transgenic Organisms; Transplantation; Xenograft procedure; allograft rejection; base; cytokine; improved; insight; macrophage; mouse model; nonhuman primate; prevent; receptor; response; stem; transgene expression

DESCRIPTION (provided by applicant): Xenotransplantation using pigs as the transplant source has the potential to resolve the growing shortage of human organ donors. The most profound barrier to xenotransplantation is the immunological rejection of the xenograft and the development of relatively non-toxic immunosuppressive or tolerance-inducting regimens is required to justify clinical trials of pig organs. CD47 is ubiquitously expressed and serves as a ligand of signal regulatory protein (SIRP)1, a key inhibitory receptor on phagocytes and APCs. Our pilot data have shown that: 1) pig CD47 cannot functionally interact with mouse or human SIRP1 and the expression of host- type CD47 on a pig hematopoietic cell line markedly inhibits its phagocytosis by xenogeneic (mouse or human) macrophages; 2) induction of mixed chimerism neither overcomes the CD47 barrier nor prevents rejection of pig hematopoietic cells by phagocytes; and 3) CD47-SIRP1 interaction is required for preventing host DC activation and inhibiting anti-donor T cell responses in mice after donor specific transfusion (DST). Based on these and other pilot data described in this application, we hypothesize that CD47 incompatibility makes xenogeneic hematopoietic cells highly susceptible to phagocytosis and augments T cell xenoreactivity by promoting APC activation; thus posing a strong barrier to xenotolerance induction by the mixed chimerism and DST approaches. To test our hypothesis, we will pursue three specific aims. Aim 1 is to evaluate the potential of CD47 transgene expression to inhibit phagocytosis of pig hematopoietic stem/progenitor cells (HSC/HPC). We will determine 1) whether mouse CD47-expressing pig HSC/HPC show reduced susceptibility to phagocytosis and improved ability to engraft in pig cytokine transgenic mice; and 2) if human CD47 expression can protect pig HSC/HPC from phagocytosis by human macrophages. In Aim 2, we will further characterize the interaction of pig CD47 with human SIRP1 (binding vs. function). We will determine: 1) if fusion proteins of pig CD47 extracellular domain can bind to human macrophage SIRP1; 2) the ability of pig CD47 to bind and signal through human SIRP1 at the cellular level; and 3) the possible role of CD47 MMS (multiply membrane-spanning) domain in determining the species specificity. In Aim 3, we will use CD47 KO mouse models to further understand how CD47-SIRP1 signaling contributes to DST-induced immunosuppression. We will determine whether the engagement of CD47 on DST donor cells with SIRP1 on recipient DCs can promote the induction of regulatory T cells by inhibiting DC activation/maturation, and if CD47 expression on donor cells is critical for the synergistic effect of DST with costimulatory blockade on tolerance induction. These studies are expected to provide insights into the mechanisms of xenoimmune responses, help in evaluating the value of making human CD47 transgenic pigs for improving xenotolerance induction by mixed chimerism and DST, and enlighten future investigations on the potential roles of other immune inhibitory receptors in xenograft rejection and xenoimmune tolerance.

描述（由申请人提供）：使用猪作为移植源的异种移植有可能解决日益严重的人体器官捐献者短缺问题。异种移植最严重的障碍是异种移植物的免疫排斥，需要开发相对无毒的免疫抑制或耐受诱导方案来证明猪器官临床试验的合理性。 CD47 广泛表达并作为信号调节蛋白 (SIRP)1 的配体，SIRP1 是吞噬细胞和 APC 上的关键抑制性受体。我们的试验数据表明：1）猪CD47不能与小鼠或人SIRP1功能性相互作用，并且宿主型CD47在猪造血细胞系上的表达显着抑制其被异种（小鼠或人）巨噬细胞的吞噬作用； 2)混合嵌合体的诱导既不能克服CD47屏障，也不能阻止吞噬细胞对猪造血细胞的排斥； 3) CD47-SIRP1相互作用是防止宿主DC激活和抑制小鼠供体特异性输血(DST)后抗供体T细胞反应所必需的。基于本申请中描述的这些和其他试验数据，我们假设 CD47 不相容性使得异种造血细胞对吞噬作用高度敏感，并通过促进 APC 激活来增强 T 细胞异种反应性；因此，对混合嵌合和 DST 方法诱导异种耐受形成了强大的障碍。 为了检验我们的假设，我们将追求三个具体目标。目的 1 是评估 CD47 转基因表达抑制猪造血干细胞/祖细胞 (HSC/HPC) 吞噬作用的潜力。我们将确定 1) 表达小鼠 CD47 的猪 HSC/HPC 是否表现出对吞噬作用的敏感性降低以及在猪细胞因子转基因小鼠中的移植能力是否提高； 2) 人 CD47 表达是否可以保护猪 HSC/HPC 免受人巨噬细胞的吞噬。在目标 2 中，我们将进一步表征猪 CD47 与人 SIRP1 的相互作用（结合与功能）。我们将确定：1）猪CD47胞外域的融合蛋白是否可以与人巨噬细胞SIRP1结合； 2) 猪CD47在细胞水平上结合人SIRP1并通过人SIRP1发出信号的能力； 3) CD47 MMS（多重跨膜）结构域在确定物种特异性中的可能作用。 在目标 3 中，我们将使用 CD47 KO 小鼠模型来进一步了解 CD47-SIRP1 信号传导如何促进 DST 诱导的免疫抑制。我们将确定DST供体细胞上的CD47与受体DC上的SIRP1的结合是否可以通过抑制DC活化/成熟来促进调节性T细胞的诱导，以及供体细胞上的CD47表达对于DST与共刺激阻断的协同作用是否至关重要关于耐受诱导。 这些研究有望深入了解异种免疫反应的机制，有助于评估通过混合嵌合和 DST 制备人 CD47 转基因猪以改善异种耐受诱导的价值，并启发未来关于其他免疫抑制受体在异种移植中的潜在作用的研究排斥和异种免疫耐受。