Immune tolerance of skin allograft transplantation induced by immature dendritic cells of a third party carrying donor antigens in mice

A review on applications of abatacept in systemic rheumatic diseases

Abatacept is a CTLA-4Ig fusion protein that selectively modulates the CD80/CD86:CD28 costimulatory pathway required for full T-cell activation. The FDA has approved it to be used to treat adult rheumatoid arthritis, juvenile idiopathic arthritis, and adult active psoriatic arthritis. Considering the vital pathogenic role of the CTLA-4 pathway in autoimmune diseases, abatacept could efficiently treat other systemic rheumatic diseases. Here we reviewed the published literature to profile the perspectives about the off-label uses of abatacept, especially in those refractory cases with inadequate responses to conventional therapies and biologic agents. Abatacept can be a promising therapeutic option and contribute to reducing hormone dependence and correlated adverse events.

ECDI-fixed donor splenocytes prolong skin allograft survival by promoting M2 macrophage polarization and inducing regulatory T cells

Rejection is a common complication of allogeneic tissue transplantation. Fixation of splenocytes (SP) with 1-ethyl-3-(3'-dimethylaminopropyl)-carbodiimide (ECDI) induces immune tolerance in recipients post-transplantation; however, the mechanism underlying this effect remains unclear. Here, we determined the mechanisms of ECDI-fixed donor SP (ECDI-SP) in inducing tolerance in skin allograft transplantation. C57BL/6-recipient mice that received Balb/c full-thickness skin transplants with two infusions of donor-derived ECDI-SP, along with rapamycin showed superior skin allograft survival and lower inflammatory cell infiltration than mice that received rapamycin-only treatment. In ECDI-SP-treated mice, the levels of anti-inflammatory cytokines such as interleukin (IL)-10 in sera were markedly increased, whereas the expression of inflammatory cytokines was significantly suppressed. Splenic macrophages were significantly polarized to the alternative activated macrophage (M2) phenotype, with expansion of CD4+Foxp3+ regulatory T cells (Tregs) in the spleen and draining lymph nodes. Allostimulatory activity of ECDI-SP in vitro and donor-specific ex vivo hyporesponsiveness were observed. C57BL/6 macrophages engulfed allogeneic Balb/c-derived ECDI-SP, polarized to the M2 phenotype, with pronounced cAMP response element-binding (CREB) protein phosphorylation. By facilitating increased IL-10 expression, ECDI-SP induced M2 polarization and Treg production, inhibiting effector T-cell proliferation. Thus, ECDI-SP modulates macrophage M2 polarization by increasing CREB phosphorylation and promoting Treg production to suppress allogeneic skin graft rejection.

Adenovirus-Mediated CCR7 and BTLA Overexpression Enhances Immune Tolerance and Migration in Immature Dendritic Cells

Our previous report revealed that immature dendritic cells (imDCs) with adenovirus-mediated CCR7 overexpression acquired an enhanced migratory ability but also exhibited the lower immune tolerance observed in more mature cells. In the present study, we aimed to investigate whether BTLA overexpression was sufficient to preserve immune tolerance in imDCs with exogenous CCR7 overexpression. Scanning electron microscopy and surface antigens analysis revealed that BTLA overexpression suppressed DC maturation, an effect further potentiated in CCR7 and BTLA cooverexpressing cells. Correspondingly, in vitro chemotaxis assays and mixed lymphocyte reactions demonstrated increased migratory potential and immune tolerance in CCR7 and BTLA coexpressing cells. Furthermore, CCR7 and BTLA cooverexpressed imDCs suppressed IFN-γ and IL-17 expression and promoted IL-4 and TGF-beta expression of lymphocyte, indicating an increase of T helper 2 (Th2) regulatory T cell (Treg). Thus, these data indicate that CCR7 and BTLA cooverexpression imparts an intermediate immune phenotype in imDCs when compared to that in CCR7- or BTLA-expressing counterparts that show a more immunocompetent or immunotolerant phenotype, respectively. All these results indicated that adenovirus-mediated CCR7 and BTLA overexpression could enhance immune tolerance and migration of imDCs. Our study provides a basis for further studies on imDCs in immune tolerance, with the goal of developing effective cellular immunotherapies for transplant recipients.

Rapamycin Combined with Immature Dendritic Cells Attenuates Obliterative Bronchiolitis in Trachea Allograft Rats by Regulating the Balance of Regulatory and Effector T Cells

BACKGROUND

Obliterative bronchiolitis (OB) ranks as the major obstacle for long-term survival of lung transplantation patients. Rapamycin (Rapa) has recently been confirmed as an immunosuppressant for antirejection due to its suppressive role in T cell activation. Here, we explore the effect of Rapa combined with immature dendritic cells (imDCs) on OB in trachea allograft rats.

METHODS

The effect of bone marrow-derived imDCs or Rapa-imDCs on lymphocyte cells and CD4+ T cells were evaluated by methyl thiazolyl tetrazolium and flow cytometry. Tracheal transplantation was performed from Lewis rats to Wistar recipients. Recipient rats received Rapa+imDCs for 10 consecutive days after implantation. Allograft rejection was assessed by micro-CT image, hematoxylin/eosinHE staining and flow cytometry. The underlying mechanism was also investigated.

RESULTS

Rapa-imDCs inhibited lymphocyte and CD4+ T cell growth. Furthermore, Rapa-imDC treatment induced T cell hyporesponsiveness by attenuating T cell differentiation into IFN-x03B3;-producing T cells (Th1), but increased CD4+CD25+Foxp3+ T cell (Treg) contents. Importantly, Rapa-imDC administration ameliorated airway obliteration symptoms and CD4+ and CD8+ T cell infiltration. Furthermore, the proinflammatory factor levels of IL-6, TNF-α, IFN-x03B3; and IL-17 were decreased, concomitant with the upregulation of immunosuppressive cytokines IL-10 and TGF-β1. Further analysis confirmed that Rapa-imDC treatment attenuated the amounts of infiltrated IL-17+CD4+ T cells (Th17 cells) and Th1 cells, but increased Treg contents in the spleens of recipients.

CONCLUSIONS

This research may corroborate a protective role of Rapa-imDCs in OB by regulating the balance between effector T cells and Tregs, suggesting a potential applicable strategy to treat OB after lung transplantation.

Immune tolerance of mice allogenic tooth transplantation induced by immature dendritic cells

As a common procedure in dentistry for replacing a missing tooth, allogenic tooth transplantation has encountered many difficulties in the clinical application because of immunological rejection. It is hypothesized that immature dendritic cell injection might be a potential alternative method to avoid or alleviate immunological rejection in allogenic tooth transplantation. To test this hypothesis, a mouse model of allogenic and autogeneic tooth transplantation was to established test the immunosuppressive effect of immature dendritic cells (imDCs) derived from donor bone marrows on transplant rejection in allogenic tooth transplantation. 2 × 10(6) imDCs generated with 50 U/ml GM-CSF were injected to each recipient mouse by two ways: tail vein injection 7 days before transplantation or regional dermal injection at day 0 and day 3 after transplantation. Groups of autogeneic tooth transplantation and allogenic tooth transplantation without any treatment were set as control groups. The effects were evaluated with histopathology and immunohistochemistry. We found there was no obvious rejection in autogeneic tooth transplantation group; tail intravenous injection group showed obviously alleviated rejection while local injection group and none-treatment allogenic tooth transplantation group both showed severe rejection. Our results suggested that the rejection of allogenic tooth transplantation could be alleviated by tail vein injection of donor bone marrow-derived imDCs though it could not be completely eliminated. The clinical application of imDCs in allogenic tooth transplantation still needs further deep research.