The dual role of IL-2 in the generation and maintenance of CD8+ memory T cells

The mechanisms responsible for the generation and maintenance of T cell memory are unclear. In this study, we tested the role of IL-2 in allospecific CD8(+) T cell memory by analyzing the long-term survival, phenotype, and functional characteristics of IL-2-replete (IL-2(+/+)) and IL-2-deficient (IL-2(-/-)) CD8(+) TCR-transgenic lymphocytes in an adoptive transfer model. We found that IL-2 is not essential for the in vivo generation, maintenance, or recall response of CD8(+) memory T cells. However, IL-2 increased the size of the CD8(+) memory pool if present at the time of initial T cell activation but reduced the size of the pool if present during memory maintenance by inhibiting the proliferation of CD8(+) memory T cells. Thus, IL-2-based vaccine strategies or immunosuppressive regimens that target IL-2 should take into account the divergent roles of IL-2 in CD8(+) T cell immunity.