IMMUNOBIOLOGY OF PANCREATIC ISLET XENOGRAFTING

临床器官和组织移植面临的一个关键难题是缺乏 供移植的供体组织。此问题需要使用 考虑来自其他物种(异种移植)的组织作为潜在的 捐献材料的替代供应。而抗体依赖 超急性排斥反应是移植的主要障碍 不协调的固体器官异种移植，细胞异种移植的排斥反应- 例如胰岛-似乎是由T细胞依赖启动的 豁免权。这项提议的目的是澄清细胞的性质 异种胰岛细胞模型的免疫/耐受 异种移植。建立异种T细胞的基本要求 免疫和耐受是指导未来临床的必要因素 细胞异种移植的应用。 对异种组织的细胞免疫的性质仍不清楚，因为 异种反应性的一个重要悖论就说明了这一点：充满活力的细胞- 异种移植的介导性排斥反应在体内发生，尽管发现 T细胞对异种抗原的依赖反应强度 随着系统发育的发展，体外呈现细胞(APC)呈减少趋势 响应物种和刺激物种之间的差距越来越大。特定的 这项提案的目标I试图通过测试 工作假说：细胞同种异体移植排斥反应严重依赖于 异种移植时“直接”(供体APC依赖)T细胞活化 排斥反应在很大程度上依赖于“间接”(宿主APC依赖)T细胞 激活。对这一假设及其影响的检验将通过以下方式进行： (1)测定未激发和激发淋巴细胞的表型(S) 和/或重建同种异体胰岛移植物抗 严重联合免疫缺陷(SCID)小鼠的异种移植免疫 检查已定义的异种反应性T细胞系/克隆的能力 体内调节异种移植免疫，(3)确定异种移植 免疫在体内受到MHC的限制，(4)确定炎症性 组织损伤在同种异体胰岛移植抗排斥中的作用 活体内，以及(5)确定异种胰岛移植物是否为供体 体内APC依赖。 在体外，异种反应的低反应性被归因于 部分，针对物种间T细胞-APC相互作用的不足。这些 影响T细胞活化的缺陷也可能影响耐受性 对异种抗原的诱导。本提案的具体目标二涉及 这个问题通过检验假设：有效的耐受性诱导 外周(胸腺外)移植抗原需要CD8或CD4联合 受体与MHC分子的相互作用。这一假设将得到检验。 通过：(1)确定成熟的T细胞是否会对 同种异体胰岛移植与异种移植的比较 MHC是有缺陷的，以及(2)确定是否通过遗传消除 CD8-I类MHC相互作用将排除外周血对MHC的耐受性 I类同种异体抗原。

A key dilemma facing clinical organ and tissue grafting is the shortage of donor tissues for transplantation. This problem requires the consideration of tissues from other species (xenografts) as a potential alternative supply of donor material. While antibody-dependent hyperacute rejection provides a major barrier to the transplantation of discordant solid-organ xenografts, the rejection of cellular xenografts - such as pancreatic islets - appears to be initiated by T cell-dependent immunity. The aim of this proposal is to clarify the nature of cellular immunity/tolerance to xenogeneic pancreatic islets as a model of cellular xenografting. Establishing the basic requirements for xenogeneic T cell immunity and tolerance is necessary for directing the future clinical application of cellular xenografting. The nature of cellular immunity to xenogeneic tissues remains unclear as illustrated by an important paradox of xenoreactivity: Vigorous cell- mediated rejection of xenografts occurs in vivo despite the finding that the intensity of the T cell-dependent response to xenogeneic antigen presenting cells (APC) in vitro tends to decrease as the phylogenetic disparity between responding and stimulating species increases. Specific Aim I of this proposal attempts to reconcile this paradox by testing the working hypothesis: Cellular allograft rejection depends heavily on 'direct' (donor APC-dependent) T cell activation while xenograft rejection depends heavily on 'indirect' (host APC-dependent) T cell activation. The test of this hypothesis and its implications will be by: (1) Determining the phenotype(s) of unprimed versus primed lymphocytes and/or antibodies necessary to reconstitute islet allograft versus xenograft immunity in severe-combined-immune-deficient (SCID) mice, (2) Examine the ability of defined xenoreactive T cell lines/clones to mediate xenograft immunity in vivo, (3) Determine whether xenograft immunity is MHC-restricted in vivo, (4) Determine whether inflammatory tissue damage contributes to islet allograft versus xenograft rejection in vivo, and (5) Determine whether rejection of islet xenografts is donor APC-dependent in vivo. The hyporeactivity of xenogeneic responses in vitro is attributed, in part, to deficiencies in the inter-species T cell-APC interaction. These deficiencies which affect T cell activation may also affect tolerance induction to xenoantigens. Specific Aim II of this proposal addresses this issue by testing the hypothesis: Efficient tolerance induction to peripheral (extrathymic) transplantation antigens requires CD8 or CD4 co- receptor interaction with MHC molecules. This hypothesis will be tested by: (1) Determining whether maturing T cells will develop tolerance to islet allografts versus xenografts where the inter-species CD8-class I MHC is deficient, and (2) Determining whether genetically eliminating the CD8-class I MHC interaction will preclude peripheral tolerance to MHC class I alloantigens.