Role of TCF7 in T cell differentiation in thymus and peripheral. In thymus, early thymic progenitor (ETP) cells undergo several stages to form mature T cells. The process can be generally divided into three stages: double negative (DN), double positive (DP), and single positive (SP). TCF7 is involved in many critical events in the process, and is essential for DN cell proliferation, DN to DP transition, DP cell survival, the positive selection and negative selection. TCF7 is also important for peripheral T cell differentiation. TCF7 promotes CD4+ T cells differentiates to Th2 cells and suppress Th1 or Th17 cells at the same time. Besides, TCF7 also facilitates the formation of memory CD8+ T cells. TCF7 transcription factor 7, ETP early thymic progenitor, DN double negative, DP double positive, SP single positive, Treg regulatory T cell.