T Cell Vaccine Induced Immune Tolerance Of Simultaneous Pancreas And Kidney Transplantation In Rat

Organ transplantation remains the ultimate rescue for terminal diseases. Immune rejection is the major cause of transplantation failure. Most patients have to take immunosuppressive drugs for life in order to inhibit rejection. However long-term use of immunosuppressive drugs causes severe health concerns including adverse effects (hypertension, hepatotoxicity or renal toxicity), severe infections and malignancies, which also reduce the long-term survival rate of the patients. Inducing tolerance to the transplanted organs while keeping normal immunity to pathogens remains the ultimate goal in the transplatation medicine.After allotransplantation, the immune system of the recipient recognizes the MHC antigen on the organs from the donor and incurs immune responses against the allograft. In this process, the allogenic reactive T cells play important roles. Vaccination with deactivated allogenic reactive T cells would induce immunotolerance or hyporesponsiveness to specific antigens. T Cell Vaccine (TCV) is vaccine developed using this strategy. Studies on autoimmune diseases suggested that immunizing animals with TCV derived from autoreactive T cells or allogenic reactive T cells would cause immune response against these T cells, which subsequently eliminate or reduce the reactivity to autoantigen or allografts.Diabetic nephropathy is the most severe and fetal complications of diabetics. 47.7% of the diabetic patients develop diabetic nephropathy in China, which is especially the case in Type I diabetics. In type I diabetic patients who have a disease progress over 20 years, 10% would have nephropathy which would progress to terminal conditions such as toxuria. Simultaneous pancreas-kidney transplantation, SPK, is the only effective treatment for these patients. In 1966, Kelly and Lillehei from the Minnesota University did the first successful SPK. Since then, the number of pancreas transplantation is increasing rapidly according to record of the UNOS and IPTR. Till Oct 2002, the total number of pancreas transplantation is 18843. Most of them were done in America(13951). In the 13330 cases of pancreas transplantations recorded by UNOS during 1987 to 2002, 78% of the patients underwent SPK. SPK is presently considered the most effective treatment for uremic type I diabetic patients. Since 1980s, safety of success rate of this procedure increased dramatically with improvement of transplantation techniques and implications of the UW conservatives and novel immunosuppressive.This study addresses the issue whether TCV could be used to induce immunotolerance in SPK. TCV was developed and characterized. Inbred AS rat, SD rat and Wistar rat were used. Splenocytes form the AS rat and SD rat were isolated and immunized into Wistar rat. Afterwards, the splenocytes from the Wistar rat were prepared, activated in vitro by ConA, reated with mitomycin and then deactivated to develop TCV. Our findings suggested that reactivity of the splenocyte of Wistar rat immunized with TCVs show decreased reactivity to ConA, indicating that nonspecific hyporesponsiveness was induced by TCVs. TCVs induced both nonspecific and specific tolerance to allogeneic antigens. TCVs induced apoptosis of peripheral T cells, and tilt the balance of CD4/CD8 ratio toward the CD8 side.Reliable animal models for simultaneous pancreas and kidney transplantation is extremely important for the study. We hereby established our model based on a STZ-induced diabetic rat model. Rats had stable biochemical indexes and pathological manifestations after the operation. The success rate of the operations was 76%. In this model, modified vascular anastomosis technique was used, which in turn greatly reduced the surgical time and complications. Internal drainage of the pancreatic fluid was adopted to meet the demand of physiological fitting.Based on the model and TCVs, we immunized the surgical model rats with TCVs developed with allogenic reactive T cells. Different timing schedules were used. Rejections or immunotolerance of rat to allografts were recorded. To investigate the therapeutic potential of the TCVs. FK506 was used as a control to observe the efficacy of the TCVs in inducing immune tolerance to allogenic organs. Our findings suggested that SCVs partially inhibited the increase of CD4/CD8 ratio, reduced serum IL-2 and TNF level and decreased expression of selectin at RNA and protein level. Based on these findings we believe that TCVs is a useful reagent for inhibiting immune rejections in SPK and may be of therapeutic potentials.Taken together, we successfully developed T cell vaccines and confirmed its efficacy of inducing immunotolerance, established a reliable surgical model of SPK, and found that TCV could induce immunoterlance to the allograft organs in SPK model. Hopefully, our finding would be some practical implications in the future.