Protein tyrosine phosphorylation in response to hIL-3 and hGM-CSF in hIL-3 R,β_c and hGM R,β_ccells, respectively. Cells were washed and incubated growth-factor free for 4 hours before stimulation with 10 ng/mL hIL-3 or hGM-CSF as appropriate for 10, 30, and 60 minutes (lanes 2, 3, 4, and 6, 7, 8, respectively). Cell lysates were prepared and resolved by SDS-PAGE using a 7.5% gel before Western blotting using an antiphosphotyrosine antibody. Lanes 1 through 4 and 5 through 8 are cell lysates prepared from hIL-3 R,β_c and hGM R,β_c cells, respectively. Lane 1 and 5 are control samples (cytokine diluent only). Arrows indicate molecular weights of the molecular-weight markers. Similar results were obtained with at least 2 clones of each transfect.