Antigen affinity, costimulation, and cytokine inputs sum linearly to amplify T cell expansion

T cell activation is a dynamic process. T cells encounter multiple input signals such as antigens, costimulatory molecules, and cytokines at different times and anatomical locations during an infection. But how do T cells integrate this information to determine the extent to which they divide? To find out, Marchingo et al. stimulated mouse T cells in culture with different combinations of inputs and also tracked antigen-specific T cell responses in mice infected with influenza virus. They found that T cells linearly sum the various stimulatory inputs they receive to determine their “division destiny.” Science , this issue p. [1123][1] [1]: /lookup/doi/10.1126/science.1260044