CD56^bright NK cell co-cultured with LPS-activated macrophages produce abundant IFN-γ.

Resting CD56^bright and CD56^dim NK cells (1 × 10⁵/well) were co-cultured with autologous macrophages (1 × 10⁵/well) and control (phosphate-buffered saline) or LPS for 72 hours, and cell culture supernatants were assayed for IFN-γ protein. CD56^brightNK cells co-cultured with LPS-activated macrophages (Mφ + LPS) produced significantly more IFN-γ protein than CD56^dim NK cells (6439.41 ± 2579.16 vs 791.5 ± 289.2 pg/mL;P < .05; n = 7). No IFN-γ protein was detected in co-cultures without LPS (Mφ) or in cultures of LPS-activated NK cells or macrophages (data not shown). ■ indicates CD56^dim; ▪, CD56^bright.