Costimulation of remission T cells by autologous AML blasts after targeting of B7-1 IgG to the tumor membrane.
(A) Expression of B7-1 on the leukemic blasts of patient no. 39 (AML-M5a) after preincubation with CD8 IgG or B7-1 IgG (5 to 10 μg/106 cells). The expression of high-affinity FcγRI was determined at the same time. (B) PBMCs of the same patient were isolated while she was in complete remission and either left untreated or preactivated with PHA as described in “Materials and methods.” AMLTC with mitomycin C–inactivated and CD8 IgG–pretreated (■) or B7-1 IgG–pretreated (▪) AML blasts was performed at an R-to-S ratio of 1:2 in the absence or presence of OKT3.3H-thymidine-uptake was measured after 48 to 72 hours of culture as described earlier. Results from triplicate cultures are given as mean ± SD. T cells (resting/preactivated) alone: 0.5 (0.08 cpm × 103/0.3 ± 0.03 cpm × 103. AML blasts (CD8 IgG/B7-1 IgG) alone: 0.3 ± 0.07 cpm × 103/0.3 ± 0.09 cpm × 103.
