Operational tolerance induced by pretreatment with donor dendritic cells under blockade of CD40 pathway

Background. Dendritic cells can mount immune response as competent antigen presenting cells. Recently, it has been reported that immature dendritic cells induce prolongation of allograft survival. However, the ability of mature dendritic cells to induce operational tolerance is unclear. Therefore, in this study, we examined the ability of splenic mature dendritic cells to induce operational tolerance to fully allogeneic antigens using mouse heterotopic heart transplantation model. Methods. CBA (H2(k)) mice received i.v. injections with donor splenic dendritic cells or B cells in the absence or presence of monoclonal antibody (mAb) specific for CD40 ligand or CD80/CD86 2 weeks before transplantation of a C57BL/10 (H2(b)) heart. Results. When donor dendritic cells were injected i.v. 2 weeks before transplantation, rejection response was accelerated compared with that of naive mice [median survival time (MST) = 7 and 8 days, respectively]. However, when CD40 pathway was blocked by anti-CD40 ligand mAb, i.v. injection of donor dendritic cells but not B cells induced indefinite graft survival (MST > 100 and 20 days, respectively). Mice treated with anti-CD40 ligand mAb alone rejected their grafts with a MST of 18 days. Intravenous injection of donor dendritic cells and B cells in combination with anti-CD80/CD86 mAbs was less effective to induce graft prolongation (MST = 9.5 and 13 days, respectively). Conclusions. Therefore, under blockade of CD40 pathway, mature dendritic cells were tolerogens in vivo independent of CD80/86 pathways.