Immunosuppressive properties of CD95L-transduced “killer” hybrids created by fusing donor- and recipient-derived dendritic cells

Abstract

IntroductionTransplantation of hematopoietic organs (eg, bone marrow) into immunocompetent hosts induces the activation of alloreactive T cells of both recipient and donor origins, thus causing the host 3 graft reactions expressed clinically as graft rejection and the graft 3 host reactions manifested as graft-versus-host disease (GVHD), respectively. It has become evident that dendritic cells (DCs) play crucial roles in the initiation of both types of alloresponses. 1,2 Host 3 graft reactions are mediated primarily by host T cells that recognize either intact donor major histocompatibility complex (MHC) molecules expressed on donor DCs (direct presentation) or donor-derived peptide antigens being presented by host DCs (indirect presentation). Likewise, donor T cells that recognize intact host MHC molecules on host DCs or host-derived peptide antigens presented by donor DCs function as main effector leukocytes for GVHD. 3,4 Both CD4 ϩ and CD8 ϩ T cells are involved in the above bidirectional allogeneic immune responses, thus providing an additional level of complicity. 5,6 Many therapies have been developed to prevent the onset of allogeneic immune responses after organ transplantation. For example, GVHD, a major complication after allogeneic bone marrow transplantation, has been prevented and treated clinically by conventional immunosuppressive agents and, in selected cases, by ex vivo removal of T cells from the donor inoculum before in vivo infusion. 7,8 GVHD in experimental animals has been successfully treated by more innovative immunomodulatory strategies that are designed to: (1) trigger clonal anergy of effector T cells by blocking costimulatory molecules 9-13 ; (2) control the expansion and differentiation of effector T cells by administration of recombinant cytokines or cytokine inhibitors 7,14-17 ; or (3) interfere with effector T-cell trafficking by blocking adhesion molecules. [18][19][20] Our ultimate goal is to develop a new strategy that is designed to selectively kill alloreactive T cells.Recently, we have created "killer" DCs by introducing the CD95L cDNA into a fully mature DC line (XS106) derived from A/J mice. 21 The resulting CD95L-transduced killer DC clone, when pulsed with ovalbumin (OVA), induced rapid apoptosis of OVA-reactive T cells and prevented the induction of delayedtype hypersensitivity (DTH) responses to OVA in syngeneic A/J mice. Likewise, contact hypersensitivity responses to dinitrofluorobenzene (DNFB) were suppressed almost completely by administration of DNFB-pulsed killer DCs. On the other hand, when administered into allogeneic BALB/c hosts, killer DCs inhibited only partially the host immune responses to A/Jassociated MHC molecules. We have interpreted these results to suggest that killer DCs may deliver apoptotic signals only to the host T cells that recognize allo-MHC molecules via direct presentation. Thus, we have hypothesized that complex alloimmune responses may be suppressed more efficiently if one can Figure 1A). Materials and methods Animals and cell linesAll ...

Incomplete Killing And Enhanced Activation of Islet-Reactive CD8+ T Cells by FasL-Expressing Dendritic Cells Limits Protection from Diabetes

“…When DC were nucleofected with pGOI2FasL, all the GFP + cells expressed equal levels of activation markers and FasL up to a detectable level (Figure 2, lower row). This was comparable to previous reports following FasL transfection [21]. .…”

“…Although we observed no such adverse side effects in our mice, our present study is reminiscent of work where beneficial effects were either incomplete or accompanied by adverse effects. In studies by Matsue et al [20,21] and Min et al [41], FasL co-expressing DC prevented delayed-type hypersensitivity reactions, allograft rejection and graft-versus-host reactions successfully.…”

“…When pulsed with antigen, these DC suppress in vivo delayed-type hypersensitivity reactions and contact hypersensitivity reactions [20]. When given together with an allogenic bone marrow transplantation, FasL-expressing DC of the same allotype prevent a graft-versus host response [21]. As several lines of evidence indicate an important role for CD8+ T cells in autoimmune diabetes [22][23][24][25], we decided to investigate the effects of a DC vaccination consisting of FasL-expressing DC on the development of diabetes during ongoing beta-cell destruction by islet-specific CD8+ T cells.…”

Mature But Not Immature Fas Ligand (CD95L)-Transduced Human Monocyte-Derived Dendritic Cells Are Protected from Fas-Mediated Apoptosis and Can Be Used as Killer APC

“…However, all these studies were performed using murine DC, B cells, macrophages, or cell lines as APC (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)39). Therefore, for future clinical application, it had to be determined whether human DC can be efficiently transduced with FasL and whether these cells would be capable of eliminating Fas ϩ target cells.…”

Gene Therapy Progress and Prospects: Gene therapy in organ transplantation

“…36 Dendritic cells have also been genetically engineered to express Fas ligand (CD95L). [37][38][39] Engagement of Fas (CD95) on the surface of T cells by CD95L leads to the induction of apoptosis in activated T cells. Apoptosis induced by CD95/CD95L interactions is thought to play a role in the establishment of immunoprivileged sites such as the eye and testis, and may be involved in the killing of CD4 T cells.…”