IFNG and influenza: IFN-γ production following NK cell stimulation with target cells or influenza was generally low and did not differ between healthy and infected subjects (median percentages with ranges after subtracting background in healthy vs. influenza-infected following stimulation with H1N1: 0.2 (0–4.3) vs. 0.7 (0.2–1.9); 221 cells: 0.4 (0–5.2) vs. 1.3 (0–2.6); K562 cells: 0.7 (0–9.8) vs. 2.8 (1.1–5.1); data not shown).