CD56^bright NK cells can use T cell–derived IL-2 to costimulate IFN-γ production when cocultured in vitro.

Sorted NK cell subsets were cocultured with a tetanus toxoid–specific T-cell clone (T) and peptide-pulsed autologous APCs plus IL-12 in the presence of neutralizing anti–IL-2 (α-IL-2) or control (Cntrl) Abs. After 48 hours cell-free culture supernatants were harvested and assayed for IFN-γ production by ELISA. The T-cell clone used does not produce IFN-γ, and thus all IFN-γ is NK cell–derived (data not shown). As a positive control, NK cells were also cultured with rIL-2 (10 pM) plus IL-12 in the presence of α-IL-2 or Cntrl Abs. Results shown are the means ± SEMs of replicate wells and summarize 6 independent experiments. *P < .03.