T Cell Factor-1 and β-Catenin Control the Development of Memory-like CD8 Thymocytes

Innate memory-like CD8 thymocytes develop and acquire effector function during maturation in the absence of encounter with Ags. In this study, we demonstrate that enhanced function of transcription factors T cell factor (TCF)-1 and β-catenin regulate the frequency of promyelocytic leukemia zinc finger (PLZF)-expressing, IL-4–producing thymocytes that promote the generation of eomesodermin-expressing memory-like CD8 thymocytes in trans . In contrast, TCF1-deficient mice do not have PLZF-expressing thymocytes and eomesodermin-expressing memory-like CD8 thymocytes. Generation of TCF1 and β-catenin–dependent memory-like CD8 thymocytes is non–cell-intrinsic and requires the expression of IL-4 and IL-4R. CD8 memory-like thymocytes migrate to the peripheral lymphoid organs, and the memory-like CD8 T cells rapidly produce IFN-γ. Thus, TCF1 and β-catenin regulate the generation of PLZF-expressing thymocytes and thereby facilitate the generation of memory-like CD8 T cells in the thymus.