The dual role of IL-2 in the generation and maintenance of CD8(+) memory Tcells

The mechanisms responsible for the generation and maintenance of T cell mem ory 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 fu nctional characteristics of IL-2-replete (IL-2(+/+)) and IL-2-deficient (IL -2(-/-)) CD8(+) TCR-transgenic lymphocytes in an adoptive transfer model. W e 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 s ize of the CD8(+) memory pool if present at the time of initial T cell acti vation but reduced the size of the pool if present during memory maintenanc e by inhibiting the proliferation of CD8(+) memory T cells. Thus, IL-2-base d vaccine strategies or immunosuppressive regimens that target IL-2 should take into account the divergent roles of IL-2 in CD8(+) T cell immunity.