Controlled major histocompatibility complex-T cell receptor signaling allows efficient generation of functional, antigen-specific CD8⁺ T cells from embryonic stem cells and thymic progenitors

Generation of early T cells by coculturing stem cells on notch-ligand-expressing OP9 stromal cells (OP9-DL1) has been widely reported. However, further differentiation of these cells into mature, antigen-specific, functional T cells, without retroviral transduction of T cell receptors (TcRs), is yet to be achieved. In the thymic niche this differentiation is controlled by the interaction of developing TcRs with major histocompatibility (MHC) molecules on stromal cells. We hypothesized that by providing exogenous antigen-specific MHC/TcR signals, stem and progenitor cells could be engineered into functional, effector T cells specific for the same antigen. Here we demonstrate that both thymus-derived immature T cells (double positive [DP]: CD4⁺CD8⁺) and mouse embryonic stem cells can be efficiently differentiated into antigen-specific CD8⁺ T cells using either MHC tetramers or peptide-loaded stromal cells. DP cells, following MHC/TcR signaling, retained elevated recombination activating gene-1 levels, suggesting continuing TcR gene rearrangement. Both DP and embryonic stem-cell-derived CD8⁺ T cells showed significant cytotoxic T lymphocytes activity against antigen-loaded target cells, indicating that these cells are functional. Such directed differentiation strategy could provide an efficient method for generating functional, antigen-specific T cells from stem cells for potential use in adoptive T cell therapy.