FIG. 4.

(A) Caspase-8 activity in undifferentiated NT2 cells. Treatments with 1, 10, 50, or 100 ng/ml of each respective protein (x axis) and percent caspase-8 activity for each treatment relative to caspase-8 activity in gp120 (100 ng/ml)-treated cell cultures, which were considered as 100% (y axis), are indicated. Jurkat T cells treated with 0.2-μg/ml doxorubicin for 48 h (positive control) exhibited a 17-fold increase in caspase-8 activity over that of control cultures. (B) Caspase-8 activity in mature, differentiated human neurons. Treatment with 1, 50, or 100 ng/ml of respective protein (x axis) and percent caspase-8 activity for each treatment relative to caspase-8 activity in gp120 (100 ng/ml)-treated cell cultures, which were considered as 100% (y axis), are shown. Jurkat T cells treated with 0.2-μg/ml doxorubicin for 48 h exhibited a 9.4-fold increase in caspase-8 activity over that of control cultures (positive control).