Figure 4. Purified rhGM-CSF demonstrates bioactivity.

Shown is the proliferation of TF-1 cells after incubation for 4 days in the presence of purified rhGM-CSF. For comparison, a commercial source of rhGM-CSF was also analyzed. TF-1 cells require the presence of GM-CSF for survival and therefore their proliferation with the addition of GM-CSF, as measured using the WST-1 reagent, is a measure of GM-CSF bioactivity. Absorbance values are proportional to the number of viable cells. Data are the mean ±SD of triplicate measurements.