Background: Donor specific tolerance to heart allografts is induced in LEW.1A rat recipient by two donor LEW.1W blood transfusions prior engraftment. Although the tolerant allograft is infiltrated by leukocytes, graft infiltrating cells are only expressing low levels of the Th1- or Th2-related cytokines suggesting that induction of tolerance is an active phenomenon in which the mechanisms remain to be elucidated.
Materials and methods: Differential display (DD) method was applied on RNAs extracted from graft infiltrating cells (GIC) derived from allografts either from rejecting untreated rats or donor-specific blood transfusion treated tolerant rats. Quantitative RT/PCR was performed to confirm mRNA expressions of the selected genes.
Results: Among the six differentially displayed DNAs (ddDNA) overexpressed in GIC from rejected allografts, the macrophage scavenger receptor-A (A:D13265) was identified; it exhibited a stricking induction of mRNA expression from day 1 to 7 after transplantation. Among the seven ddDNAs overexpressed in GIC from tolerant allografts, the 3-hydroxy-3-methyl glutaryl coenzyme-A reductase (A:M29249) and an "unknown gene" (ddDNA EC9) were identified and both were confirmed to be up-regulated by quantitative RT/PCR.
Conclusions: The relevance of these genes in transplantation has not yet been reported and must therefore be elucidated; they represent possible targets for immunointervention. Nevertheless, our data demonstrate that the DD is a powerful tool to identify new genes involved in organ transplantation.