The immune suppressive effect of induced regulatory T cells expressing C/EBPβ in allogenic skin graft transplantation

Abstract

The selective immunosuppression by induced regulatory T (iTreg) cells has the potential to protect transplanted tissue without sacrificing immunity against other infections, greatly enhancing the chances of successful engraftment. However, the relative instability of Foxp3 expression in iTreg cells, and consequently their immunosuppressive function, deters the development of therapeutic iTreg cells at present. Results from a recent study have identified C/EBPβ as a transcription factor that enables stable expression of Foxp3 even in the presence of inflammatory cytokines IL-4 and IFN-γ (Lee, 2014). In the light of such findings, the present research investigated the immunosuppressive function of iTreg cells expressing C/EBPβ in the context of allogenic skin transplantation. For this purpose, a protocol for culturing retrovirally-transduced iTreg cells in high purity was established by using the MIN retroviral expression vector and naïve CD4+ T cells from Foxp3eGFP-reporter mice. Highly purified populations of iTreg cells were obtained by selecting for hNGFR and GFP double-positive cells. Immunodeficient Rag-/- mice reconstituted with a 1:1 ratio mixture of naïve CD4+ T cells (CD4+CD45RBhigh) and CD8+ T cells were used as a model of T cell-mediated allogenic rejection response. Compared to control or transfer of control iTreg cells, the transfer of iTreg cells expressing C/EBPβ showed possibility of delay in the rejection of allogenic grafts. Through macroscopic observation and analysis during the rejection response, the efficacy of iTreg cells expressing C/EBPβ in suppressing the immune response against allogenic graft will continue to be evaluated. The future findings of this study will contribute to the development of iTreg cells as a safe and reliable immunosuppressive therapy.