IMMUNOGENICITY OF A XENOGENEIC BIOARTIFICAL LIVER

肝衰竭是一个严重的问题，每年影响成千上万的美国人。一种新的治疗形式，生物人工肝（BAL），正在开发中，以提供肝功能衰竭患者在移植之前或直到恢复天然肝脏。含有猪肝细胞或人C3A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，并限制了装置的功能和治疗的持续时间。肝细胞死亡的机制尚不清楚，可能是由免疫介导的损伤引起的。根据这一假设，首次接触BAL时的免疫激活可能导致随后接触BAL时的加速反应。虽然BAL含有一层膜来阻止患者循环与装置中的非自体肝细胞的接触，但膜上的孔允许抗原物质从BAL中释放出来，并允许患者排斥反应的分子介质进入。以下三个假设将作为本研究的具体目的进行检验：(1)BAL中肝细胞的死亡是通过免疫介导的机制发生的；(2)二次暴露时，受者对BAL治疗的免疫反应增强；(3)受体的免疫应答对BAL的功能有不利影响。对BAL的免疫反应将以受体抗体滴度、细胞活化和细胞因子表达的变化为特征。BAL治疗后肝细胞的组织学和生化检查将确定BAL中细胞死亡的机制。将测量BAL中肝细胞活力和受体蛋白沉积，并用于评估BAL中免疫反应的影响。BAL将在健康狗身上进行测试，以提供正常的初级免疫反应，并在第一次治疗后三周进行第二次BAL治疗。将比较平均孔径为200纳米和5纳米（大约100 kD分子量截止）的中空纤维膜，因为这些孔径与当前BAL的临床试验有关。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.