IMMUNOBIOLOGY OF PANCREATIC ISLET XENOGRAFTING

临床器官和组织移植面临的一个关键困境是缺乏 用于移植的供体组织 这个问题需要 考虑其他种属的组织（异种移植物）作为潜在的 替代供应的供体材料。 虽然抗体依赖性 超急性排斥提供了移植的主要障碍， 不协调的实体器官异种移植，细胞异种移植的排斥反应， 如胰岛-似乎是由T细胞依赖性的 免疫力 该提案的目的是澄清蜂窝的性质， 异种胰岛细胞免疫耐受模型 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条件。 细胞异种移植的应用。 异种组织的细胞免疫的性质仍不清楚， 说明了一个重要的矛盾异种反应：充满活力的细胞- 尽管发现异种移植物介导的排斥反应在体内发生， T细胞对异种抗原依赖性应答的强度 体外提呈细胞（APC）随着系统发育而减少， 响应物种和刺激物种之间的差异增加。 具体 本提案的目的一试图通过测试 工作假设：细胞同种异体移植排斥反应在很大程度上取决于 异种移植时的“直接”（供体APC依赖性）T细胞活化 排斥反应在很大程度上依赖于“间接”（宿主APC依赖性）T细胞 activation. 对这一假设及其影响的检验将通过： (1)确定未致敏与致敏淋巴细胞的表型 和/或重建胰岛同种异体移植物所必需的抗体， 严重联合免疫缺陷（SCID）小鼠的异种移植免疫，（2） 检查确定的异种反应性T细胞系/克隆的能力， 在体内介导异种移植物免疫，（3）确定异种移植物 免疫在体内是MHC限制性的，（4）确定是否炎性 组织损伤导致胰岛同种异体移植物与异种移植物的排斥反应 体内，和（5）确定胰岛异种移植物的排斥反应是否是供体 体内APC依赖性。 体外异种反应的低反应性归因于， 部分原因是种间T细胞-APC相互作用的缺陷。 这些 影响T细胞活化的缺陷也可能影响耐受性 诱导异种抗原。 本提案的具体目标二： 这个问题通过测试的假设：有效的耐受诱导， 外周（胸腺外）移植抗原需要CD 8或CD 4共表达。 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T细胞是否将发展对以下的耐受性： 胰岛同种异体移植物与异种移植物相比， （2）确定是否通过基因消除MHC缺陷， CD 8-I类MHC相互作用将排除对MHC的外周耐受 I类同种抗原。

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.