Intragraft gene and protein expression in rat liver allografts treated with costimulatory blockade alone or in combination with CyA

Background. Costimulatory blockade has been shown to prevent acute rejection (AR) and promote long-term graft survival in a number of animal models including nonhuman primates. The effect of concomitant administration of conventional immunosuppressives on long-term liver allograft survival and intragraft expression of immune mediators has not previously been examined.Materials and methods. A high-responding Dark Agouti to Lewis orthotopic liver transplant (LEW OLT) model was used to compare anti-CD154 alone, or in combination with cyclosporin (CyA) on allograft survival. Donor-specific reactivity was assessed by mixed lymphocyte reaction (MLR) and allogeneic skin grafts. Surviving rats were euthanized on day 150 and intragraft gene (CD80, 86, 152, 154, IFN-γ, IL-2, IL-6, IL-10, IL-13, TNF-α, TGF-β, IL-7, Fas-ligand, Granzyme B, bax, and bcl2) and protein (CD4, CD8, ED1, CD154, CD80, CD86) expression was measured.Results. Untreated control recipients had a median survival time of 5 days. Recipients treated with anti-CD154 survived to beyond 150 days with no evidence of AR. Concomitant administration of CyA did not alter the long-term survival. There was no difference in the serum aspartate aminotransferase between treatment groups or a change over time. All treated recipients showed a reduction in donor-specific MLR at day 40 and 60 but had persistence of donor reactivity to skin grafts at day 100. Histologically, liver architecture was well preserved despite the presence of a nondestructive mononuclear cell infiltrate. Analysis of intragraft gene expression revealed an inverse relationship between the duration of anti-CD154 therapy and the gene expression of costimulatory molecules and Th1 cytokine transcripts. The pro-apoptotic gene, bax, was increased in recipients treated with anti-CD154, but not CyA, compared with normal liver.Conclusions. These data demonstrate that anti-CD154 therapy either alone or in combination with CyA allows for the long-term survival of liver allografts in the rat despite there being a difference in the intragraft gene and protein profile. [Copyright &y& Elsevier]