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: 7741758
• 负责人: YONG-GUANG YANG
• 金额: $ 9.81万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 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 2010-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7741758
• 关键词: Binding; Budgets; CD47 gene; Cell Line; Cells; Chimerism; Clinical Trials; Data; Development; Extracellular Domain; FUS-1 Protein; Family suidae; Future; Hematopoietic; Human; Immune; Immunosuppression; Immunosuppressive Agents; In Vitro; Investigation; Ligands; Membrane; Modification; Mus; Organ; Organ Donor; Phagocytes; Phagocytosis; Predisposition; Published Comment; Regimen; Regulatory T-Lymphocyte; Role; SHPS-1 protein; Signal Transduction; Source; Species Specificity; Stem cells; Study Section; T cell response; T-Lymphocyte; Testing; Text; Transfusion; Transgenic Mice; Transgenic Organisms; Transplantation; Xenograft procedure; base; cytokine; improved; insight; macrophage; member; mouse model; 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）：使用猪作为移植来源的异种移植有可能解决人类器官供体日益短缺的问题。异种移植的最大障碍是异种移植物的免疫排斥反应，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的临床试验是合理的。CD47普遍表达，并作为信号调节蛋白（SIRP）1的配体，SIRP 1是吞噬细胞和apc的关键抑制受体。我们的前期数据表明：1)猪CD47不能与小鼠或人SIRP1相互作用，宿主型CD47在猪造血细胞系上的表达显著抑制其被异种（小鼠或人）巨噬细胞吞噬；2)诱导混合嵌合既不能克服CD47屏障，也不能阻止猪造血细胞被吞噬细胞排斥；3)在小鼠供体特异性输血（DST）后，需要CD47-SIRP1相互作用来阻止宿主DC激活和抑制抗供体T细胞反应。基于这些和本申请中描述的其他中试数据，我们假设CD47不相容性使异种造血细胞对吞噬高度敏感，并通过促进APC激活来增强T细胞的异种反应性；因此，通过混合嵌合和DST方法诱导异种耐受性形成了强大的障碍。为了验证我们的假设，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）吞噬的潜力。我们将确定1)小鼠表达cd47的猪HSC/HPC是否降低了对吞噬的敏感性，并提高了在猪细胞因子转基因小鼠中的移植能力；2)人CD47表达是否能保护猪HSC/HPC免受人巨噬细胞的吞噬。在Aim 2中，我们将进一步表征猪CD47与人类SIRP1的相互作用（结合vs功能）。我们将确定：1)猪CD47胞外结构域融合蛋白能否与人巨噬细胞SIRP1结合；2)猪CD47在细胞水平上结合并通过人类SIRP1发出信号的能力；3) CD47 MMS（多膜跨越）结构域在确定物种特异性中的可能作用。在Aim 3中，我们将使用CD47 KO小鼠模型来进一步了解CD47- sirp1信号如何参与dst诱导的免疫抑制。我们将确定CD47在DST供体细胞上与受体DC上的SIRP1结合是否可以通过抑制DC激活/成熟来促进调节性T细胞的诱导，以及CD47在供体细胞上的表达是否对DST与共刺激阻断对耐受诱导的协同作用至关重要。这些研究将有助于深入了解异种免疫反应的机制，有助于评估制备人CD47转基因猪对混合嵌合和DST诱导异种免疫耐受的价值，并为进一步研究其他免疫抑制受体在异种移植排斥和异种免疫耐受中的潜在作用提供启示。