A cellular calculus for signal integration by T cells

During an immune response numerous receptor-mediated signals delivered to T cells direct their proliferation, survival and differentiation. Here, we d escribe a quantitative model and in vitro methods for assessing the "calcul us" used by T cells to process these multiple signals, The model reveals ho w T cells convert independently received signals into linear additive effec ts on division times which, in turn, amplify T cell number exponentially,Th ese results explain why so many ligands can each appear obligatory for T ce ll activation and argue for a re-examination of the two-signal theory as th e basis for decisions between tolerance and activation.