IMMUNOGENICITY OF A XENOGENEIC BIOARTIFICAL LIVER

肝衰竭是一个严重的问题，每年影响美国成千上万的人。 一种新的治疗形式，生物人工肝（BAL），正在开发中，以在移植前或直到天然肝脏恢复之前为肝功能衰竭患者提供肝功能。 含猪肝细胞或人C3 A细胞的BAL的初步试验结果令人鼓舞，但仍需改进。 例如，细胞死亡发生在BAL灌注期间，并限制装置功能和治疗持续时间。 肝细胞死亡的机制知之甚少，可能是免疫介导的损伤所致。 根据这一假设，首次BAL暴露期间的免疫激活可能导致后续BAL暴露期间的加速反应。 尽管BAL含有膜以阻断患者的循环和装置中的非自体肝细胞的接触，但膜中的孔允许抗原性物质从BAL释放以及来自患者的排斥分子介质进入。 将检验以下三个假设作为本研究的特定目的：（1）BAL中肝细胞的死亡是通过免疫介导的机制发生的;（2）接受者对BAL治疗的免疫应答在二次暴露期间增加;（3）接受者的免疫应答对BAL的功能产生不良影响。 对BAL的免疫应答将通过受体中抗体滴度、细胞活化和细胞因子表达的变化来表征。 BAL中细胞死亡的机制将通过BAL治疗后肝细胞的组织学和生化检查来确定。 将测量肝细胞活力和BAL中受体蛋白的沉积，并用于评估BAL中免疫应答的影响。 将在健康犬中检测BAL，以提供正常的初次免疫应答，并允许在首次给药后3周进行第二次BAL给药。 将比较平均孔径为200 nm和5 nm（约100 kD截留分子量）的中空纤维膜，因为这些孔径与当前的BAL临床试验相关。 更好地了解受者的免疫反应将改善BAL治疗。

Liver failure is a serious problem that effects thousands of people in the United States each year. A new form of therapy, the bioartificial liver (BAL), is in development to provide liver function to patients with liver failure prior to transplantation or until recovery of the native liver. Results of preliminary trials of a BAL containing pig hepatocytes or human C3A cells have been encouraging, but improvement is still necessary. Cell death, for example, occurs during perfusion of the BAL and limits device function and the duration of therapy. The mechanism of hepatocyte death is poorly understood, and may result from immune-mediated injury. According to this hypothesis, immune activation during a first BAL exposure may cause an accelerated response during subsequent BAL exposures. Though the BAL contains a membrane to block contact of the patient's circulation and non-autologous hepatocytes in the device, pores in the membrane allow the release of antigenic material from the BAL and the entrance of molecular mediators of rejection from the patient. The following three hypotheses will be tested as specific aims of this study: (1) the death of hepatocytes in the BAL occurs by an immune-mediated mechanism; (2) The immune response of recipients to BAL therapy is increased during secondary exposures; (3) The immune response of the recipient adversely effects the functionality of the BAL. The immune response to the BAL will be characterized by changes in antibody titers, cellular activation, and cytokine expression in the recipient. The mechanism of cell death in the BAL will be determined by histological and biochemical examination of hepatocytes after BAL therapy. Hepatocyte viability and deposition of recipient proteins in the BAL will be measured and used to assess the effects of immune response in the BAL. The BAL will be tested in healthy dogs to provide a normal, primary immune response and to allow a second BAL treatment three weeks after the first treatment. Hollow fiber membranes with mean pore diameter of 200 nanometer and 5 nanometer (approximately 100 kD molecular weight cut-off) will be compared, since these pore sizes are relevant to current clinical trials of the BAL. A better understanding of the immune response in recipients will improve BAL therapy.