IL-15 produced and trans-presented by DCs underlies homeostatic competition between CD8 and {gamma}{delta} T cells in vivo.

Homeostatic mechanism by which peripheral T-cell subsets are maintained in vivo remains largely unknown. Using a T-cell proliferation model under lymphopenic settings, we now demonstrate that gammadelta T cells limit CD8 T-cell expansion but not the initial proliferation after transfer into lymphopenic recipients. Interleukin-15 (IL-15) produced by and trans-presented on the membrane of the CD11c(+) dendritic cells (DCs) is the key factor that mediates homeostatic competition between CD8 and gammadelta T cells, revealing previously unrecognized IL-15-dependent homeostatic mechanisms between different T-cell subsets in vivo.