Fig. 4. Phenotype of expanded ts21 and ts21-MafB myeloblast clones. FACS profiles of representative ts21 or ts21-MafB myeloblast clones stained with antibodies against the myeloid markers 4M12 and cIa (MHC II) (A), 61.8 and 22.3 (B) and 51/2, the erythroid markers JS3 and JS4 and the multipotent progenitor/thrombocytic marker MEP21 (C). (D) Dependence of ts21 or ts21-MafB myeloblast clones on the avian myeloid growth factor cMGF. The rate of DNA synthesis in six ts21 and six ts21-MafB myeloblast clones was determined, culturing an equal number of cells in the absence or presence of recombinant cMGF for 48 h, pulse labeling with [³H]thymidine and measuring the radioactivity incorporated into DNA. Error bars indicate the SEM.