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ASSESSMENT OF MICROCHIMERISM IN LIVER TRANSPLANTATION: INVOLVEMENT OF CLASS II HLA-DRB1 AND -DQB1 ALLELES, MICROCHIMERISM, REJECTION AND SURVIVAL.
Margareth B. Araujo, Doctorate Student , Luis-Sergio Leonardi Doctor , Ilka F.S.F. Boin, Doctor , Luis A. Magna, Doctor , Eduardo A. Donadi, Doctor and Maria-Helena S. Kraemer, Doctor . Campinas S
o Paulo, Brazil, Universidade Estadual de Campinas - Unicamp, 13000-000, Clinical Pathology Department - Immunogenetics Transplant Laboratory ; Campinas So Paulo, Brazil, Universidade Estadual de Campinas - Unicamp, 13000-000, Department of Surgery ; Campinas So Paulo, Brazil, Universidade Estadual de Campinas - Unicamp, 13000-000, Department of Genetics and Ribeiro Preto So Paulo, Brazil, Medical School of Ribeiro Preto, 13000-000, Immunology Molecular Laboratory of the Clinical Hospital .
The presence of donor-derived hematopoietic cells in blood and several tissues of organ recipient is called microchimerism and has proved to be a mechanism that induces a allograft tolerance. Therefore, in this study we analyzed the presence or absence of allogeneic microchimerism and incidence of specific alleles in patients with rejection crises, as well as related to survival time of transplanted patient. The polymorphism of HLA-DRB1 and HLA-DQB1 loci was performed in 50 liver transplant recipients and their 50 potential donors, as well as in 100 healthy controls genetically unrelated. Analysis of microchimerism was obtained thorough polymerase chain reaction using sequence-specific primers (PCR/SSP). Microchimerism was identified through nested PCR/SSP. Data obtained show that microchimerism was present in 72% of patients and we found a significant association to rejection (p=0,05). A decrease in the frequencies of alleles DRB1*01 (p=0,001), DRB1*04 (p=0,03), and DQB1*03 (p=0,001) was observed which turned out to be statistically significant when associated with rejection and survival. Further, a significant increase of the allele DRB1*15 (p<0,05) was detected in deceased patients in relation to healthy controls. These results show that the alleles DRB1*01, DRB1*04, and DQB1*03 might represent an acceptance and protection factor for the allograft, whereas the allele DRB1*15 represents a survival risk for liver transplant patients. Microchimerism seems to be one out of several immunological mechanisms which determine survival of graft.