Figure 6.

Recovery from down-regulation of surface binding. Heteromeric clone A105 was treated with 10 ng/ml GM-CSF for 4 h at 37°C. Cells were acid stripped and returned to 37°C in DMEM supplemented with 5% FBS (□), 5% FBS plus 1.0 μg/ml actinomycin D (•), or 5% FBS plus 20.0 μg/ml cycloheximide (○). At the indicated times, specific ¹²⁵I-labeled GM-CSF binding (100 pM) was determined after a 2-h incubation at 4°C. Percent binding of control is the ratio of specific binding observed after each treatment time to specific binding found in cells initially down-regulated. The data represent the mean ± SEM of three or four independent experiments done in duplicate. Analysis of variance between the 8-h FBS alone and 8-h FBS plus actinomycin D points showed no statistical difference (p = 0.13).