Upregulation and downregulation of c-kit protein expression in TF-1S, parental TF-1, and M-07e cells is shown by anti–c-kit antibody binding (YB5.B8) and FACS analysis (histograms). (A) Upregulation and downregulation of c-kit protein expression in stroma-dependent TF-1S #MB6 clone. (1) TF-1S #MB6 labeled with mouse IgG isotype control antibody; (2) TF-1S #MB6 on MS-5; (3) TF-1S #MB6 maintained for 40 hours in suspension with GM-CSF and then rexposed for 10 hours to stroma; (4) TF-1 grown in suspension with GM-CSF; (5) TF-1S #MB6 maintained for 48 hours in suspension with GM-CSF. (B) Downregulation of c-kit protein expression in M-07e on exposure to stroma cells. (1) M-07e cells labeled with mouse IgG isotype control antibody; (2) M-07e, 21 days on MS-5; (3) M-07e, 14 days on MS-5; (4) M-07e, 7 days on MS-5; (5) M-07e grown in suspension with IL-3. (C) Downregulation and upregulation of c-kit protein expression in the parental TF-1 cells. (1) TF-1 labeled with mouse IgG isotype control antibody; (2) TF-1 on MS-5; (3) TF-1 grown in suspension with GM-CSF; (4) TF-1, 14 days on stroma and then cultured for 48 hours in suspension with GM-CSF.