| Blood transfusion is an effective method in clinical treatment, it plays a very important role in saving lives during war and sudden accidents. But current blood supply can not meet the demand of transfusion, furthermore, the risk of introducing pathogen through transfusion and the problem of rare blood types as well as blood compatibility were existed. It is very important to explore inexhaustible resource for human blood substitutes and to develop universal blood type or blood group O RBC that can be transfused to recipients of any blood group .Methoxypolyethylene glycol (mPEG) is a neutral, non-toxic polymer that has been covalently grafted to proteins, biomaterials and cell surfaces as a means of improving biocompatibility and reducing immunological recognition. The mPEG derivatives such as mPEG-BTC, mPEG-ALD and mPEG2-NHS can covalently bind to e- amino- terminal groups of lysine residues in red blood cell membrane proteins. The attachment of mPEG to cell surface may prevent the interactions of large molecules such as antibodies with RBC, and thus the agglutination decreased. Our experiments showed that, comparing with mPEG-ALD and mPEG2-NHS, mPEG-BTC is the most effective material for RBC camouflage. And furthermore, the covalent modification of RBC surfaces with mPEG-BTC effectively obscures antigenic determinants while leaving the RBC structurally and functionally normal and nonimmunogenic. The serological and biochemical characterization of blood group A, B and AB hRBC modified with right amount of mPEG-BTC human are similitude to normal human red blood cell of group O. However, the sedimentation rate of mPEG-BTC modified hRBC was significantly diminished. To study the safety assessment of transfusion with mPEG modified monkey RBC(mPEG-rRBC), we havecovalently bound mPEG to the surface of Rhesus monkey RBC(like human B blood group), mPEG could cover rRBC like B antigen. Transfusion of mPEG modified like B rRBC to like A Rhesus monkey had no harmful effects on the recipient. It suggested that mPEG modified RBC could be transfused into experimental animals safely.The recent finding indicates that the serological and biochemical characterization of porcine erythrocytes share many similarities with human red blood cell (hRBC). The scientists believed that humanized porcine red blood cell(pRBC) could be used as one alternative blood source for blood human transfusion .It was reported that the main difference between pRBC antigen and hRBC antigen were aGal antigen (epitope: Galal, 3 Gal {31, 4GluNAC-R) as well as the non-aGal antigen. The aGal epitope is mainly responsible for hemagglutination of pRBCs by xenoreactive antibodies preformed in human serum and may result in hyperacute rejection of xenotransfusion from porcine to human, hi order to eliminate aGal antigen on the surface of pRBC, Recombinant soybean a-Ga!actosidase(rSa-GaIE) constructed by our lab was used to remove terminal aGal residues from aGal antigen. The results showed that the carbohydrate structures of aGal xenoantigen of pRBC treated with rSa-GalE were completely modified the same as those of human blood antigens, That is to say , aGal xenoantigen of pRBC were humanized successfully. In addition to aGal xenoantigen, there is evidence for the presence of human natural antibodies against non-aGal xenoantigen. The immunological rejection caused by non-aGal xenoantigen should not be ignored as well. On the basis of hRBC modification with mPEG-BTC, with optimization of reaction buffer,time and temperarure,The antigenic determinants of aGal and non-aGal xenoantigen on the surface of pRBC were successfully camouflaged through mPEG-BTC modification, but this modification needed higher concentration of mPEG-BTC which could cause slight structure damage. Considering this, with combination of aGal xenoantigen conversion by rSa-GalE and chemical camouflage of non-aGal xenoantigen with lower concentration of mPEG-BTC,the antigenic determinants of pRBC were attenuated and hemagglitination were diminished. The morphology,structures, fu...
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