Post-activation NK cells express high levels of cytokines.

<p>Spleen cells from control <i>Rag1^-/-</i> mice (left) and from B16-bearing <i>Rag1^-/-</i> mice (right) were incubated for 5 h in brefeldin A and stained for extracellular NK1.1 and CD25 and for intracellular cytokines. Little cytokine expression was observed in control NK cells and in CD25 h in brefeldin A and stained for extracellular NK1.1 and CD25 and for intracellular cytokines. Little cytokine expression was observed in control NK cells and in CD25⁻ NK cells from B16-bearing mice. In contrast, most CD25⁺ NK cells from B16-bearing mice had generated IFNγ, IL-10, GM-CSF and TNFα. Data were reproducible in three independent experiments.