Fig. 3. Dose-response (A) and time course (B) of ALK tyrosine phosphorylation in 2-C4 cells. For dose-response analysis, 2-C4 cells were treated with increasing concentrations of mAb16-39 (0, 0.12, 0.4, 1.2, 4, 12, 40, and 120 nM) for 5 minutes at 37°C. As a contr ol, parental NIH 3T3 cells were treated with 12 nM mAb for 5 minutes. For time-course analysis, cells were incubated with 4 nM mAb16-39 for the periods indicated (0, 2, 5, 15, 60, and 180 minutes and 24 hours). As controls, 2-C4 or parental NIH 3T3 cells were treated with 4 nM control IgG for 24 hours or 4 nM mAb for 5 minutes, respectively. ALK immunoprecipitates were probed with anti-PY antibody RC20-HRP (PY) and then reprobed with anti-ALK antibodies (ALK). The positions of 220-, 140-, and 85-kDa ALK bands are indicated by arrowheads.