| Organ transplantation has been used to treat many kinds of diseases in the terminal stage and gained epochal progress, but the graft rejection after transplan- tation has strongly restricted its development and its long-dated curative effect, and remains the main obstacle of transplantation medicine. Along with the development of immunology and molecular biology, our knowledge has been deepened on the immunological mechanisms of transplantation rejection, and lots of experimental researches have been undergone about inducing transplantation tolerance, controlling acute and chronic rejection, overcoming the side effects of the immunosuppressive drugs. So long as the true transplantation tolerance is not achieved, each step leading to an improvement of rejection will be of benefit for organ transplantation. -Melanocyte stimulating hormone(a-MSH) is a neuropeptide which is derived from the precursor molecule pro-opiomelanocortin. As its crucial role of defervescence, anti-inflammation and immunomodulation, a-MSH is becoming a hotspot in neuroendocrino-immune modulation field. It has been shown that a-MSH could restrain many kinds of acute and chronic inflammation by controlling the release of inflammatory mediators and their following effects, yet there isn't a report about the cumulation toxicity of a-MSH. In this research, we used the heterotopic cervical allo-cardiac transplantation model in mice with Cuff technique to investigate the effects of a-MSH in transplantation immunity, and studied its regulation on the development and function of dendritic cell(DC) to elucidate the mechanisms underlying the action of a-MSH on transplantation rejection.In part one, we selected 6~8 weeks, male BALB/c mice as donors and C57BL/6 mice as recipients and established Cuff model of mouse heterotopic cervical heart transplantation. Models were divided into four groups:(1)PBS control;(2)a-MSH 25 g;(3) a-MSH 50 g; (4) a-MSH 100Mg. One hour before operarion, the recipients were administered a-MSH ip once a day for 7 days. The function of the transplanted hearts were monitored by palpation and electrocardiography. On day8 post transplantation, the allografthearts were harvested to examine the histological exchanges. On day5 and day8 after transplantation, the spleen T cells were employed to analyze mixed lymphocyte reaction(MLR) and the cytokine secretion. The blood samples from the tail vein were collected at different time to determine the cytokine level. The results showed that the survival time of transplanted hearts in three a-MSH groups was markedly longer than that in PBS contol(8.50 0.61 days), especially the allograft survival time in a-MSH 50 g group was prolonged to 15.33 0.50 days. In three a-MSH groups the histological changes of transplanted hearts were improved in inflammatory cell infiltration, vascular endothelial cell swelling, cardiac muscle cell degeneration, and necrosis could hardly be seen. The histological damages were lightest in a-MSH 50 g group. T cells derived from recipients treated with a-MSH exhibited lower MLR. In these T cells, IL-2 and IFN- secretion decreased significantly, while IL-4 and IL-10 increased markedly. Serum cytokine level also showed the same change from Th1 to Th2 type.In the second part, DCs from bone marrow were cultured with GM-CSF and IL-4 and treated with different concentrations of a-MSH(10-9,10-10,10-11,10-12,10-13mol/L) for different days(day1~7 or day5~7). Then the number of DCs were counted and IL-12 secretion was detected. The phenotypes of DCs were analyzed using FACS. Allogenic T cells proliferation and their cytokine secretion were analyzed after stimulated by a-MSH-treated DCs and the antigen-presenting capacity of DCs were measured. The ultrastructure of DCs were observed by electron microscope. The results showed that a-MSH reduced the number of cultured DCs , depressed IL-12 secretion of DCs, declined the expression of CD86,CD80,Iab and CD40 on DCs.CD54 and CD 106 on DCs showed no distinct change. Furthermore, the a-MSH-treated DCs showed lower allogen...
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