Prevention of Acute and Chronic Allograft Rejection by Combinations of Tolerogenic Dendritic Cells

HMGB1 is involved in chronic rejection of cardiac allograft via promoting inflammatory-like mDCs

Chronic rejection that leads to diffuse narrowing and occlusion of graft vessels is the most important cause of morbidity and mortality following cardiac transplantation. The role and underlying mechanism of high-mobility group box 1 (HMGB1), as an established inflammatory mediator in acute rejection, remains poorly understood in chronic rejection. Here, we assessed the effects and mechanisms of HMGB1 on the chronic rejection using single MHC Class II-mismatched mouse cardiac transplantation model. It was found that HMGB1 was increased accompanying with the development of chronic rejection, while blockade of HMGB1 with specific neutralizing mAb substantially ameliorated chronic rejection-mediated vasculopathy and fibrosis of allograft, as well as markedly decreased T cell infiltration and production of IL-17A and interferon-gamma in allograft and recipient's spleen. Further, anti-HMGB1 antibody treatment significantly declined the number and frequency of mature dendritic cells (DCs) in allograft and recipient's spleen, especially CD11b(+) Ly6C(high) matured DCs that share the phenotypes with inflammatory-DCs. These findings indicate that HMGB1 contributes to chronic rejection, and HMGB1 blockade may be a novel mean to disrupt the proinflammatory loop after heart transplantation.

Expression of HSPA12B in acute cardiac allograft rejection in rats

HSP70 may play a more important role in regulating antigen-specific immune response than other HSPs; however, HSPA12B production in transplanted heart remains obscure, which was identified as the newest member of the HSP70 family. In the current study, we performed a heart transplantation model in adult rats and investigated the dynamic changes of HSPA12B expression in the cardiac grafts. The cardiac grafts of allogeneic (Wistar-Lewis rat) and syngeneic (Lewis-Lewis rat) rat models were subjected to histopathological and immunohistochemical analyses for HSPA12B expression on days 0-7 after operation. We also examined the expression profiles of active caspase-3, whose changes were correlated with the expression profiles of HSPA12B. Our results demonstrated that HSPA12B protein exhibited biphasic patterns in transplanted heart. The first expression phase correlated with ischemical reperfusion injury over 2 days post-transplant. The second peak of HSPA12B expression was found only in allografts on day 5, concurrent with the expression of caspase-3. Immunohistochemical assay showed that compared with rare expression in isografts, there were significant protein expressions of HSPA12B and caspase-3 in heart allografts from day 5 to 7 post-transplant. Furthermore, double immunofluorescence staining for active caspase-3 and HSPA12B in isografts and allografts at day 5 post-transplant were analyzed and colocalization of HSPA12B/active caspase-3 was detected in allografts. In conclusion, this is the first description of HSPA12B expression in acute cardiac allograft rejection. Our results suggested that HSPA12B might play crucial roles in heart pathophysiology after transplantation.

Adoptive transfusion of tolerance dendritic cells prolongs the survival of cardiac allograft: a systematic review of 44 basic studies in mice

BACKGROUND AND OBJECTIVE

Tolerogenic DCs (Tol-DCs), a group of cells with imDC phenotype, can stably induce T cells low-reactivity and immune tolerance. We systematically reviewed the adoptive transfusion of Tol-DCs induced by different ways to prolong cardiac allograft survival and its possible mechanism.

METHOD

MEDLINE (1966 to March 2011), EMbase (1980 to March 2011), and ISI (inception to March 2011) were searched for identification of relevant studies. We used allogeneic heart graft survival time as endpoint outcome to analyze the effect of adoptive transfusion of Tol-DC on cardiac allograft. By integrating studies' information, we summarized the mechanisms of Tol-DC in prolonging cardiac grafts.

RESULTS

Four methods were used to induce Tol-DC in all of the 44 included studies including gene-modified, drug-intervened, cytokine-induced, and other-derived (liver-derived & spleen-derived) DCs. The results showed that all types of Tol-DC can effectively prolong graft survival, and the average extension of graft survival time for each group was as follows: 22.02 ± 21.9 days (3.2 folds to control group) in the gene modified group, 25.94 ± 16.9 days (4.3 folds) in the drug-intervened groups, 9.00 ± 8.13 days (1.9 folds) in the cytokine-induced group, and 10.69 ± 9.94 days (2.1 folds) in the other-derived group. The main mechanisms of Tol-DCs to prolong graft survival were as follows: (1) induceT-cell hyporeactivity (detected by MLR); (2) reduce the effect of cytotoxic lymphocyte (CTL); (3) promote Th2 differentiation; (4) induce Treg; (5) induce chimerism.

CONCLUSION

For fully MHC mismatched allogeneic heart transplant recipients of inbred mouse, adoptive transfusion of Tol-DC, which can be gene-modified, drug-intervened, cytokine-induced, spleen-derived or liver-derived, can clearly prolong the survival of cardiac allograft or induce immune tolerance. Gene-modified and drug-induced Tol-DC can prolong graft survival most obviously. Having better reliability and stability than drug-induction, gene-modification is the best way to induce Tol-DCs at present. One-time intravenous infusion of 2 × 10(6) Tol-DC is a simple and feasible way to induce long-term graft survival. Multiple infusions will prolong it but increase the risk and cost. Adoptive transfusion of Tol-DC in conjunction with immunosuppressive agents may also prolong the graft survival time.

IDO-competent-DCs induced by IFN-γ attenuate acute rejection in rat liver transplantation

PURPOSE

We established a stable rat model of liver transplantation using Sprague-Dawley rats and Wistar rats in order to investigate the role of the IDO gene in acute rejection after rat liver transplantation.

METHODS

IDO gene expression and IDO enzyme activity were quantified in liver syngeneic grafts and allografts using microdialysis-HPLC. Liver allografts were evaluated for IDO expression by histopathology. We measured liver function-related biomarkers in liver allografts which were re-infused with untreated or IFN-γ-treated dendritic cells (DCs).

RESULTS

We found a significant increase in IDO gene expression and IDO enzyme activity in liver allografts compared the sham and syngeneic graft groups. There was a significant correlation between the number of IDO-positive cells and severity of acute rejection. IDO gene expression and enzyme activity was upregulated in the IFN-γ-treated DC group within 7 days after transplantation compared to the untreated DC group and survival rates were significantly improved.

CONCLUSIONS

Our results suggested that IDO gene expression correlates with the severity of acute rejection and that IFN-γ-induced IDO-positive DCs may attenuate acute rejection and catalyze local tryptophan metabolism via IDO enzyme expression, leading to immune tolerance after liver transplantation.