| One of the greatest barrieres in tissue and organ transplantation is alloimmunity. How do we solve the alloimmunity caused by transfusion, one kind of tissue transplantation in essence, is the focal point for domestic and oversea scholars. There are many ways to overcome this problem, such as suppressing immunal function of recipientes, revoming donor's antigens or recipiente's antibodies causing alloimniunity, cutting off the way of activating complements and so on. The comprehensive use of these ways may improve survival time of graft in recipiente. The method of chemical modification, using mPEG to camouflage antigens on the surface of cells and organs, may be the easy way to avoid the attack of immunal system. Up to now, there are, at home and abroad, no reportes on the HLA, the major factor to cause immunal rejection, camouflaged by mPEG to fake the immunal system and avoid alloimmunity. Our study first attache importance to chemical modification to find the way to camouflage HLA antigens and overcome the alloimmunity, and we draw the conclusion that the special immunal reaction between HLA angigens and their antidobies could be completely blocked via the modification of mPEG, and the technique could be used in the study of platelet in common use.1. Studies on methodTo search the optimal method of the modification of mPEG to block the special immunal reaction between HLA antigens and their antibodies. Three kinds of mPEG (mPEG-SPA, mPEG-BTC, mPEG-MAL) were used in various temperature, pH and PS to camouflage HLA-A2 antiges on the surface of lymphocytes. The effect of modification was detected by microlymphocytotoxicity test, and the optimal method was conclued by factorial experiment. The results showed that mPEG-BTC at 22癈, in PS(pH=7.4) the concentration gradient method was the optimal way to camouflage HLA antigens. In such condition HLA-A2 antigens on thesurface of lymphocytes could be camouflaged, and special immunal reaction between HLA antigens and their antibodies could be blocked completely.2. Effect on the function of lymphocyteTo research the effects of HLA-1,11 antigens and cluster of differentiation antigens (CD) camouflaged by mPEG-BTC, the lymphocte was selected to act as target for observing, and the functions of lymphocyte camouflaged by mPEG-BTC were evaluated as well. The effect of modifictaoin of HLA-1,11 antigens was detected by microlymphocytotoxicity test and one way mixed lymphocyte culture. The morphology of lymphocytes camouflaged by mPEG was observed by transmission electron microscope, and the function of proliferation, differentiation and secretion of lymphocyte was detected by lymphocyte transformation test and the IL-2 sandwich enzyme-linked immunosorbent assay (ELISA). The ability of antigen reaction of lymphocte was detected by the variation of CD. The lifetime of lymphocyte was evaluated by culture in vitro at 22. The effect of toxicity of mPEG-BTC on the genetic material was detected by karyotype analysis. After the modification of mPEG-BTC on lymphocyte, the special recognition between HLA and its ligand could be blocked, and the function of proliferation and secretion of lymphocyte is suppressed. But there is no marked discrepancy on the morphology, lymphocyte lifetime and chromatosome.3. Studies on the molecular mechanism of modificationTo study the mechanism of the various effects of HLA antigen camouflaged by different mPEG The ability of modification was detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The mechanism of modification was depicted by the three-dimensional (3D) structure of HLA antigen. The specific reaction between HLA-A2 antigens and their antibodies could be blocked by mPEG-BTC completely and by mPEG-SPA partly, but HLA antigens could not be camouflaged by mPEG-MAL. This diversity of the modification of HLA antigen camouflagedby varying mPEGs is closely associated with the amides displaying on the surface of HLA antigen. mPEG-MAL could combine with amino-3-mercaptopropionic acid which is almost enclosed...
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