Figure 4.

Down-regulation of chimeric receptor surface binding. Individual clones A120αIβI (•), A122αIIβII (○), A105αIβII (▪), and A110αIIβI (□) were treated with 10 ng/ml (520 pM) GM-CSF for the indicated times. Cells were acid stripped, and specific surface binding of 100 pM radiolabeled GM-CSF was determined after a 2-h incubation at 4°C with or without a 25-fold excess of unlabeled GM-CSF. Percentage of control binding is calculated as the percent of zero time (no prior GM-CSF treatment) specific binding. Each curve represents the mean ± SEM of three independent experiments assayed in duplicate.