Adequate responsiveness of CD8+ T cell populations is of utmost importance for the efficacy of many vaccines and immunotherapeutic strategies against intracellular pathogens and cancer. In this study, we show in mouse models that the relative number of IL-2–producing cells within Ag-specific CD8+ T cell populations predicts the population expansion capacity upon challenge. We further demonstrate that IL-2 producers constitute the best responding subset. Notably, we show that elevated production of IL-2 by CD8+ T cells results in concomitant improved population expansion capacity and immunity. The amount of IL-2 produced on a per-cell basis essentially connects directly to the superior CD8+ T cell population expansion. Together, our findings identified that autocrine IL-2 production operates in a dose-dependent fashion to facilitate the expansion potential of Ag-specific CD8+ T cell populations, which may instigate ways to augment therapies depending on fit CD8+ T cells.