Fold increase in allostimulatory capacity of AML-APCs as compared to AML blasts. Non-cultured AML blasts and cultured AML-APCs were irradiated and co-cultured with peripheral blood mononuclear cells for 5 days at 1:5 stimulator/responder (S/R) ratio. For each patient, the ratio between the [3H] thymidine incorporation by the AML-APCs and the uncultured blasts was calculated. Mean fold increased T cell stimulatory capacity and SEM are depicted. No significant differences between serum-free cultured and serum-enriched cultured AML-APCs were found. CI-cultured AML-APCs cultured in SP were significantly better stimulators of T cell proliferation as compared to AML-APCs cultured in CG medium (P=0.002) (asterisk). B Allostimulatory capacity of serum-free cultured AML-APCs as compared to FCS cultures. Non-cultured AML blasts and cultured AML-APCs were irradiated and co-cultured with peripheral blood mononuclear cells for 5 days at 1:5 S/R ratio. For each patient, the difference between serum-free cultures and standard FCS cultures, set at 100%, was calculated. Mean differences (%) and SEM are depicted. CI-cultured AML-APCs cultured in SP were significantly better stimulators of T-cell proliferation as compared to AML-APCs cultured in CG medium (P=0.049) (asterisk). Considering the total group of patients, negative controls did not show [3H] thymidine incorporation [counts per minute (cpm), median, range] (responder cells: 483, 68–1088; stimulator cells 132, 53–290) whereas significantly higher responses were observed in the co-cultures (uncultured blasts: 2,723, 312–18,720, P=0.004; FCS-cytokine culture: 5,934, 1,583–21,000, P=0.001; SP-cytokine culture: 4,003, 576–24,000, P=0.002; CG-cytokine culture: 4,235, 1,290–9,299, P=0.001; FCS-CI culture: 10,098, 699–38,184, P=0.005; SP-CI culture: 13,761, 2,168–44,565, P=0.002; CG-CI culture: 3,230, 621–15,018, P=0.03). FCS FCS-containing medium (cytokine culture n=14, CI culture n=13), SP StemSpan serum-free medium (cytokine culture n=18, CI culture n=16), CG CellGro serum-free medium (cytokine culture n=10, CI culture n=8). Note In Fig. 3A, UPN 15 is left out from the analysis of the cytokine culture in SP medium since no control blast culture could be performed.