DC-mediated stimulation of IFN-γ secretion by NK cells corresponds to the expression levels of DC tmTNF and NK-cell tmTNFRs. (A) Unstimulated fiDCs and fNK cells. (B) LPS-stimulated fmDCs and fNK cells. (C) IL-2–stimulated fiDCs and faNK cells. (D) LPS- and IL-2–stimulated fmDCs and faNK cells. (E) Unstimulated ciDCs and caNK cells. (F) LPS-stimulated cmDCs and caNK cells. The fiDCs and fNK cells (A-D) and ciDC and caNK cells (E-F) were incubated either alone (DC, NK) or together (DC+NK) in a 1:1 ratio without (A,C,E) or with (B,D,F) 200 ng/mL LPS and/or without (A-B,E-F) or with (C-D) 6000 IU/mL IL-2 for 24 hours. At the end of these cultures, cell-culture–conditioned media were assessed by IFN-γ ELISA. Data are from 1 representative experiment of 2 to 12 similar experiments performed. The results are means ± SD of triplicates IFN-γ nanograms per 0.5 × 106 cells per milliliter. Asterisks indicate significant increases in IFN-γ secretion in DC+NK-cell cocultures versus DC or NK-cell cultures alone.
