Fig. 4.

NK cell cytotoxicity induced by TLR9-stimulated pDCs is inhibited by gp120. pDCs were treated with CpGs in the presence or absence of an R5 gp120 monomer (a) or trimer (b). Stimulated pDCs were added to homologous NK cell cultures. NK cells cultured in the absence of pDCs were included as a control. PKH67-K562 target cells were added to cultures at ratios: 1:2, 1:1, and 2:1 (NK:K562). Frequency of cell killing was determined by flow cytometric measurement of the number of K562 cells staining positively for PKH67-green and propidium iodide. NK cytotoxicity is reported as the percentage of dead K562 cells calculated by subtracting in each condition the percentage of dead cells of the untreated control (K562 cultured without NK cells). SDs were calculated on the replicates.