CD11chigh dendritic cell ablation impairs lymphopenia-driven proliferation of naive and memory CD8+ T cells

The peripheral lymphocyte pool size is governed by homeostatic mechanisms. Thus, grafted T cells expand and replenish T cell compartments in lymphopenic hosts. Lymphopenia-driven proliferation of naive CD8(+) T cells depends on self-peptide/MHC class I complexes and the cytokine IL-7. Lymphopenia-driven proliferation and maintenance of memory CD8(+) T cells are MHC independent, but are believed to require IL-7 and contact with a bone marrow-derived cell that presents the cytokine IL-15 by virtue of its high affinity receptor IL-15R alpha. In this study we show that optimal spontaneous proliferation of grafted naive and memory CD8(+) T cells in mice rendered lymphopenic through gene ablation or irradiation requires the presence of CD11C(high) dendritic cells. Our results suggest a dual role of CD11c(high) dendritic cells as unique APC and cytokine-presenting cells.