Fig. 2.

Full NK cell activation induced by Pf-RBC requires monocytes/macrophages. (A) Purified or FACS-sorted NK cells were exposed to medium alone (0), 3D7-RBC, or RBC for 24 h. (Upper) CD69 expression by NK cell assessed by flow cytometry (mean ± SEM of 10 experiments). (Lower) CXCL8 production in the supernatant of culture (mean ± SEM of 3 experiments). (B) After 4 h of exposure to RBC infected with 3D7 strain, in the presence of suboptimal doses of IL-12, the frequency of IFN-γ-producing NK cells was assessed by flow cytometry. In each experimental condition, the IFN-γ production was calculated as the proportion of IFN-γ-producing NK cells subtracted from background, as compared with IFN-γ-producing NK cells within PBMC in the presence of Pf-RBC (this “100% value” corresponds to 8.4% in this representative experiment). Purified NK cells were cultured alone or together with purified autologous DC, plasmacytoid DC (Upper) or FACS-sorted monocytes (Lower). CD14⁺ monocytes were also depleted from PBMC by FACS sorting before stimulation (Lower, NK in PBMC w/o monocytes). One representative experiment of three is shown.