Overview of CD8 T cell immunity regulated by IL-2 and IL-7. The receptor for IL-7 is expressed on the naïve and memory T cells including precursors cells; common lymphoid progenitors (CLP), double-positive, and single-positive thymocytes, and recent thymic emigrants (RTE). IL-7 is mainly produced by stromal cells and gives a signal to IL-7Rα-expressing cells to regulate their survival, proliferation, and maintenance. By contrast, the IL-2 receptors are highly induced on activated T cells after antigenic stimulation and the cells themselves also become a major producer of IL-2. After rapid expansion, the effector T cells develop into different fates depending on the amount of IL-2 signaling. Cells expressing high levels of IL-2Rα receive strong IL-2 signaling and become short-lived effector cells showing increased expression of Blimp1, KLRG1, and cytolytic activity. Cells expressing low levels of IL-2Rα receive relatively weak IL-2 signaling and become memory precursor cells showing increased expression of IL-7Rα, CD62L, IL-2 production, and proliferation capacity but decreased expressions of effector-associated molecules above. The re-expression of IL-7Rα on memory T cells capable of maintaining the long-term survival of the cells.
