Induction of immune tolerance to rat liver allograft by sTNFRI-IgGFc and CCR 7 gene modified immature dendritic cells

Background: Dendritic cells (DC) are the most powerful antigen presenting cells, which play key roles in recognition and presentation of antigens, initiation of immune response, initiation of immune rejection and induction of immune tolerance. DC is a heterogeneous group of cells, the immature dendritic cells (imDC) mainly induce immune tolerance, while mature dendritic cells (mDC) can initiate inflammation or immune rejection. Soluble tumor necrosis factor receptor I (sTNFRI) can competitively bind with TNF-α, block the biological function of TNF-α, as a result to negatively regulate the imDC activation induced by TNF-α. Recent studies suggest that imDC which migrate to the secondary lymphoid organs plays an important role in the induction of immune tolerance. The interaction of chemokine and chemokine receptor 7 (CCR7) on DC surface is the main driving force and pathway for the migration of peripheral DC to lymphoid tissues. Studies have indicated that the enhanced CCR7 expression may promote the imDC migration to lymphoid organs, thereby inducing immune tolerance. Based on the establishment of a rat model of liver transplantation rejection, this study aims to investigate the role of sTNFRI-IgGFc fusion gene and CCR7 gene co-modified imDC in liver graft immune tolerance. Methods: Bone marrow cells from rats were isolated, obtained imDC by vitro induction or mDC by treatment with TNF-α. The imDC infected by empty vector virus, carrying sTNFRIIgGFc, CCR7 gene of the virus alone or together. After TNF-α induction, the expression of CD80 and CD86 was detected, the chemotaxis ability was detected by Transwell. To establish a rat liver transplantation rejection model, and 7 days before surgery, intravenous infusion PBS, empty vector virus, imDC carrying sTNFRI-IgGFc, CCR7 gene virus alone or co-infected to mice, the levels of alanine transaminase (ALT) and total bilirubin (Tbil) in the serum were measured; the acute rejection score was compared; the survival time of each group was compared; the levels of IL-2, IFN-γ, IL-4 and IL-10 in serum were measured by Elisa method. Results: TNF-α could significantly increase the expressions of CD86 and CD80 on the surface of imDC. STNFRI-IgGFc gene modification can significantly weaken the effect of TNF-α on the up-regulation of the expressions of CD80 and CD86 on the surface of imDC, so as to block the maturation and differentiation of imDC. CCR7 gene modification can significantly up-regulate the expression of CCR7 protein in imDC cells, and enhance its ability of chemotactic migration. Intravenous infusion of sTNFRI-IgGFc or CCR7 genetically modified imDC to recipient rats before liver transplantation can significantly reduce the post operative serum ALT and Tbile contents, decrease the acute liver rejection score, and prolong the survival time of the recipient rats. Furthermore, infusion of sTNFRI-IgGFc and CCR7 gene co-modified imDC can more improve the liver function, reduce the acute rejection of rats, and prolong the survival time after operation. Intravenous infusion of sTNFRI-IgGFc and (or) CCR7 genetically modified imDC can significantly reduce the contents of inflammatory cytokines IL-2 and IFNin the recipient rats, and increase the contents of anti-inflammatory cytokines IL-4 and IL-10 simultaneously. Conclusion: sTNFRI-IgGFc and CCR7 gene co-modified imDC can induce immune tolerance in liver transplantation recipient rats, reduce the graft rejection, and prolong the survival time effectively.