T cell cytolytic capacity is independent of initial stimulation strength

How cells respond to a myriad of stimuli with finite signaling machinery is central to immunology. In naive T cells, the inherent effect of ligand strength on activation pathways and endpoints remains controversial, confounded by environmental fluctuations and intercellular variability within populations. Here, we study how ligand potency affects CD8(+) T cell activation in vitro using genome-wide RNA, multi-dimensional protein and functional measurements in single cells. Our data reveal that strong ligands drive more efficient and uniform activation than weak ligands, but all activated cells are fully cytolytic. Importantly, activation follows the same transcriptional pathways, regardless of ligand potency. Thus, stimulation strength does not intrinsically dictate T cell activation route or phenotype; instead it controls how rapidly and simultaneously cells initiate activation, allowing limited machinery to elicit wide-ranging responses.