CD27 is required for generation and long-term maintenance of T cell immunity

The Traf-linked tumor necrosis factor receptor family member CD27 is known as a T cell costimulatory molecule. We generated CD27(-/-) mice and found t hat CD27 makes essential contributions to mature CD4(+) and CD8(+) T cell f unction: CD27 supported antigen-specific expansion (but not effector cell m aturation) of naive T cells, independent of the cell cycle-promoting activi ties of CD28 and interleukin 2. Primary CD4(+) and CD8(+) T cell responses to influenza virus were impaired in CD27(-/-) mice. Effects of deleting the gene encoding CD27 were most profound on T cell memory, reflected by delay ed response kinetics and reduction of CD8(+) virus-specific T cell numbers to the level seen in the primary response. This demonstrates the requiremen t for a costimulatory receptor in the generation of T cell memory.