Characterization at the single-cell level of naive and primed CD8 T cell cytokine responses

The aim of this study was to characterize differences between naive and pri med CD8 T cells. Our results show that (i) naive and primed CD8 T cells dis play similar activation thresholds, with no direct evidence for a differenc e in their TCR signals, and (ii) primed cells differ mainly in their capaci ty to secrete IFN-gamma. A comparison of the two populations at the single- cell level demonstrated that the increased production of IFN-gamma, by the primed cell subset is due to a larger proportion of single cells that are a ble to synthesize this cytokine early following activation. These results i ndicate that the intrinsic effector capabilities of individual CD8 T cells expressing the same TCR are heterogeneous and that cells with identical ant igen specificity but increased effector capacities are generated or selecte d during the primary response. (C) 2000 Academic Press.