IMMUNOGENICITY OF A XENOGENEIC BIOARTIFICAL LIVER

肝功能衰竭是一个严重的问题，每年影响着美国成千上万的人。一种新的治疗形式，生物人工肝(BAL)正在开发中，以在移植前或在天然肝脏恢复之前为肝功能衰竭患者提供肝功能。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的灌流过程中，限制了设备的功能和治疗持续时间。肝细胞死亡的机制尚不清楚，可能是免疫介导的损伤所致。根据这一假设，在第一次BAL暴露期间的免疫激活可能会在随后的BAL暴露中引起加速反应。尽管BAL包含一层膜，以阻止患者循环与装置中非自体肝细胞的接触，但膜上的孔允许BAL释放抗原物质，并允许患者进入排斥反应的分子介质。本研究将检验以下三个假设：(1)BAL中肝细胞的死亡是通过免疫介导的机制发生的；(2)在二次暴露期间，受者对BAL治疗的免疫反应增强；(3)受者的免疫反应对BAL的功能产生不利影响。对BAL的免疫反应将以受体体内抗体效价、细胞激活和细胞因子表达的变化为特征。BAL的细胞死亡机制将通过BAL治疗后肝细胞的组织学和生化检查来确定。肝细胞活性和受体蛋白在BAL中的沉积将被测量并用于评估BAL中免疫反应的效果。BAL将在健康的狗身上进行测试，以提供正常的初级免疫反应，并允许在第一次治疗三周后进行第二次BAL治疗。我们将比较平均孔径为200纳米和5纳米(截留分子量约为100 kD)的中空纤维膜，因为这些孔径大小与当前的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.