Large-scale induction and expansion of a novel human alloantigen-specific CD8 regulatory T cells

Abstract

Although recent studies have been focused on CD4+ regulatory T cells (Treg), CD8+Treg have also been reported to play important roles in the induction and maintenance of immune tolerance. Adoptive transfer of CD8+Treg in rodents or induction of CD8+Treg in human can prevent or treat allograft rejection and autoimmune diseases. However, no approaches have been reported for the generation of human antigen-specific CD8+Treg at a practical scale for clinical use. Here, we found that two novel CD8+T-cell subsets with different levels of CD8 surface expression: CD8high and CD8low, could be induced from naïve CD8+precursors in vitro by allogeneic CD40-activated B cells, whereas only CD8high T cells were alloantigen-specific Treg with relatively poor alloantigen-specific cytotoxicity. Importantly, alloantigenspecific CD8high Treg could be induced and expanded from naïve CD8+CD25-T cells at a large scale after 3 weeks of culture without exogenous cytokines. These induced alloantigen-specific Treg were CD45RO+and CCR7− memory cells, and expressed Foxp3, CD25, CD27, CD28, and CD62L. The induction and expansion of CD8high Treg by CD40-activated B cells were dependent on endogenously expressed IFN-γ, IL-2, IL-4 and CTLA-4. This approach may facilitate the clinical application of CD8+Treg-based immunotherapy in transplantation and autoimmune diseases.