A combination of anergic cells' adoptive transfer and rapamycin therapy prolongs cardiac allograft survival in mice

Transferable cardiac allograft acceptance induced by transfusion of donor B cells with impaired inducible costimulator/B7h allorecognition

OBJECTIVE

Donor-specific transfusion (DST) of leukocytes with an impaired costimulatory signal has been proven to be an effective way to improve allograft survival. Inducible costimulator (ICOS) has been shown to play a crucial role in acute and chronic allograft rejection. To test the role of ICOS signaling during DST, we employed ICOS-Fc-targeted B cells as antigen of DST to challenge the allogeneic engraftment in vivo.

MATERIALS AND METHODS

A murine cardiac allograft model was employed using BALB/c donors and C57BL/6 recipients, while various transfusions were performed according to treatment protocols.

RESULTS

Allograft survival was prolonged by infusion of ICOS-Fc-targeted B cells; however, allograft acceptance could not be achieved unless additional systemic injections of ICOS-Fc were given. Adoptive transfer of splenic CD4(+) but not CD4(+)CD25(-) subsets from long-term allograft survival (LTAS) mice to lightly irradiated naive recipients resulted in subsequent BALB/c allograft acceptance without additional immunosuppression.

CONCLUSIONS

ICOS/B7h signaling during direct allorecognition played an important role in prolonging allograft survival, and an allograft acceptance can be established by DST with complete blockade of ICOS/B7h in both direct and indirect allorecognition. Interestingly, this allograft acceptance was transferable and maintained at least partly by the immune regulation of CD4(+)CD25(+) T cells. These findings may help to design a potential therapeutic treatment to prevent allograft rejection by DST in combination with ICOS/B7h blockade.

Immunomodulatory drug FTY720 induces regulatory CD4(+)CD25(+) T cells in vitro

As a novel immunosuppressant, FTY720 (2-amino-2-(2-[4-octylphenyl] ethyl)-1, 3-propanediol hydrochloride) has been used to prevent the allograft rejection in organ transplantation. FTY720 can prolong markedly survival of the allograft by inducing apoptosis of reactive lymphocytes and by redirecting the homing of lymphocytes. However, as the archetype of a new class of immune modulators, the potential effect of FTY720 on the immune response needs to be elucidated further. In this study, FTY720 was added into the mixed lymphocyte reaction (MLR) consisting of murine splenocytes from BALB/c and C57BL/6, to observe its direct effect on the induction of CD4(+)CD25(+) regulatory T cells. It was demonstrated that the proportion of CD4(+)CD25(+) and CD4(+)CD25(+)forkhead box P3 (FoxP3)(+) T cells in MLR were increased significantly by FTY720 treatment, and the expression of FoxP3 mRNA in lymphocytes was also enhanced markedly by the drug. A synergetic effect was observed between FTY720 and co-stimulation blockades. Moreover, analysis of the function of FTY720-treated cells manifested an increased suppressive activity in an in vitro antigen-specific proliferation assay. In conclusion, FTY720 can increase the number and enhance the functional activity of CD4(+)CD25(+) regulatory T cells in MLR, and these FTY720-treated cells possess the activity to down-regulate the alloreactivity of lymphocytes, indicating its potential use for therapeutic purposes.