Bioassays of possible stimulatory factors in Dami/HEL and Meg-01 conditioned medium. Mo7e cells, pretreated for 18 hours in medium without cytokines, were incubated for 72 hours with control or conditioned medium from cultures of Dami/HEL cells (A) or Meg-01 cells (B), using either (1) culture medium not exposed to Dami/HEL or Meg-01 cells (CTL), (2) conditioned medium collected from the 3-day culture of Dami/HEL or Meg-01 cells (CM), or (3) conditioned medium plus 2 ng/mL GM-CSF (CM + GM-CSF). The cells then were labeled with [³H]-TdR for an additional 4 hours. CPM of [³H]-TdR incorporation was determined from triplicate samples and expressed as the mean. These results are representative of three separate experiments.