Impaired allogeneic T-cell priming by IVIg-DCs occurs only in the presence of NK cells. (A) Indicated numbers of immature blood DCs were stimulated with TNFα and IL-1β for 18 hours in the absence (CTRL-DC, —) or presence of 10 mg/mL IVIgs (IVIg-DC, –). The next day, DCs were washed, and allogeneic T cells, which contained 12% NK cells, or the same number of allogeneic T cells without NK cells were added. Proliferation was assessed after 5 days by determination of the incorporation of [³H] thymidine (N = 4; *P < .05, **P < .01, paired Student t test). Error bars are SD. (B) Purified allogeneic T cells and NK cells labeled with CFSE were added and subsequently cultured with CTRL-DCs (left) or IVIg-DCs (right) at a DC/T/NK ratio of 1:48:12. At day 6 of coculture, cells were labeled with CD3-PE and CD56-APC, and the CFSE dilution profile of CD3⁺CD56⁻ T cells was analyzed using ModFit software. CFSE analysis was also performed on CD56⁺CD3⁻ NK cells, which is shown in Figure 7A separately. (C) The same experiment, as depicted in panel B, but CFSE-labeled allogeneic T cells without NK cells, were cultured with CTRL-DCs (left) or IVIg-DCs (right) at a DC/T ratio of 1:48. Proliferation index (PI) and percentage of precursor T cells (% Prec) depicted in panels B,C are means plus or minus SD from 4 independent experiments.