Figure 3.

IL15 infusions sensitize NK cells to respond with cytokine production. PBMCs were stimulated with PMA/Ionomycin (A), IL12/IL18 (B), or coincubated with NK target cells (C), and intracellular cytokine amounts were determined by FACS on gated CD56^dim (CD3⁻/CD16⁺/CD56^dim) or CD56^bright (CD3⁻/CD56^bright) NK cells. IL15 infusions caused increases of IFNγ,TNFα, and GM-CSF productions in PMA/Ionomycin- or IL12/IL18-responding NK cells within the CD56^bright subset. Within the CD56^dim subset, IFNγ production was increased after IL12/IL18 stimulation. CD56^bright NK cells also acquired the ability to respond to target cell exposure by cytokine production after IL15 infusions, whereas little change was seen for target cell–exposed CD56^dim NK cells. D shows that IL15 infusions had increased the expression of surface IL18 receptor on CD56^dim NK cells to levels lower than those on CD56^bright NK cells. We observed no IL12 receptor expression changes. Analyses were done once on each of 5 patients. Graphs depict mean + SD. *, P < 0.05 and **, P < 0.01.