CD40/IL-2 Immunotherapy induces massive expansion of bystander memory CD8+ cells and anti-tumor effects are CD8 dependent.

<p>Three C57BL/6 mice per group were treated with IT or PBS/rIgG (control) and effects on CD8+ T cell expansion were quantified by flow cytometric analysis 11 days after the initiation of therapy. For <i>in vivo</i> tumor studies one million 3LL cells were administered by s.c. injection into the flank of C57BL/6 mice seven days prior to initiation of therapy. Six to eight 3LL bearing mice were treated with IT and/or CD8+ T cell depletion to examine CD8+ dependence of anti-tumor effects. (<b>a</b>) Gating strategy for bystander memory CD8+ CD44^high NKG2D+ CD25− cells. (<b>b–e</b>) Expansion of bystander memory CD8+ T cells in the spleen and lymph nodes of IT or vehicle treated mice expressed as total numbers (<b>b,c</b>) or as a percentage of total CD8+ T cells (<b>d,e</b>). Effects of IT and/or CD8 depletion on tumor growth (<b>f</b>) and survival (<b>g</b>).