Pilot Study of the Effects of Liver Specific Antigen on Immunoreactions in Liver Allotransplantation
|Keywords||Liver specific antigen alloimmunoresponse transplantation immunology lymphocyte apoptosis|
Since liver transplantation and hepatocyte transplantation have been beneficial measurement for certain end-stage hepatopaty, an understanding of hepatocyte immunogenicity may allow interventions to promote liver and hepatocyte engraftment and /or prevent rejection. Although MHC-antigens were extensively studied, liver transplant rejection and posttransplantation hepatopathy were not completely resolved. Liver transplantation is not strictly for MHC matching of donors and recipients, and grafted livers and recipients can survive for long a long time after immunotherapy. On the other hand, although multiple MHC loci matching in some cases, grafted liver functionally loss and rejection taken place, suggesting that HLA matching may have dualistic effects. No satisfactory explanations about the phenomenon were made out heretofore and most studies limited in MHC antigens themselves and conclusions remained controversial, which suggest that apart from MHC antigens, other antigen systems may play roles in liver transplantation immunoreaction and determine posttransplantation results.There are specific functional cells distinguishing to others in each tissue or organ. These cells should express specific proteins to meet the demands of their specific functions. On the other hand, althoughsome proteins are universally expressed, the expression levels differ from one kind of cell to others, thus formatting an antigen system called tissue specific antigen that is independent of HLA, ABO antigen system and has polymorphism too.The specific antigens only expressed in liver cell membrane or liver cytoplasma and encoded by loci not linked to the MHC gene were called liver specific antigen (LSA). It was reported that this antigen can be detected in sera of almost all liver allotransplantation recipients but its effects remained unknown yet. Thus in this experiment, we direct the aim to find whether LSA have alloimmunogenicity to induce alloimmunoreaction and its possibility to be an important transplantation antigen using different LSA immunization pathways. The possible mechanisms involved were preliminarily discussed in this reseach too.Materials and MethodsThirty Lew rats were randomly divided into five groups (6 per group). Group I : PBS-thymus or portal vein injected group. There were no differences in the parameters tested between PBS-thymus and PBS-portal vein injected rats. Group II :Rats were each inoculated in the hind footpads with 1 mg of F344 LSA emulsified in an equal volume of Freunds complete adjuvant(lOOul). Additional 1 mg of LSA in Freunds incomplete adjuvant(lOOul) were given on weeks 2, 3 and 4.GroupIII: Portal vein immunization of 10 mg of F344 LSA by portal vein injection. Group IV :Thymus immunization of 10 mg F344 LSA by thymus injection. Group V :Rats were given 150mg/kg of cyclophosphamide by intraperitoneal route. All rats were sampled seven days after treatments. Mixed lymphocyte culture, mixed lymphocyte hepatocyte culture, Western blotting, DNA gel electrophoresis and TUNEL were employed to analyze the status of peripheral and central lymphoid organs.ResultsCompared with control group in MLC, the OD value of the experimental groups decreased no significantly except that of CY treated group which showed significantly low (p<0.01). This datashowed that LSA immunization couldn’t result in the changes of MLC that detects reaction of lymphocytes to MHC antigens. Compared with control group, the OD value of MLHC group II ,III and IV decreased significantly (p<0.05) after 7 days LSA immunization , but didn’t decrease to the level of that of group V. DNA ladders and caspase-3 were detected in group II ,III and IV as well as group V, indicating the existence of apoptosis. Furthermore, the number of apoptotic cells increased significantly in CY treated group as well as portal vein and thymus immunized one.DiscussionThe results of MLC and MLHC after LSA immunization suggested that antigen specific lymphocytes didn’t lose the ability to immunoresponse to allo-MHC antigen.