Impaired allostimulatory properties of DCs derived from HIV-1–infected patients. Highly purified myDCs and pcDCs at increasing concentrations were cocultured for 6 days with 10⁵ allogeneic T lymphocytes. Incorporation of [³H]thymidine was measured for the last 16 hours of culture. The stimulation indices were determined by dividing the proliferation induced in the presence of DCs by the proliferation seen in culture with no DCs added (background). In all experiments, the backgrounds were fewer than 600 counts per minute. The maximum stimulation index for each of 17 HIV-1–infected patients (▦) was compared with 6 uninfected controls (□, panel A). Medians, 25th and 75th percentiles (boxes), and 10th and 90th percentiles (bars) are shown. Median stimulation indexes of pcDCs (panel B) and myDCs (panel C) from controls and patients at all concentrations of DCs are shown. Titrating progressively increasing numbers of DCs into the MLR produced different dose-response curves in controls (panel D) and patients (panel E). *P < .05, **P < .01, Mann Whitney U test.