TNF-α induces proliferation of HCD57 cells, and a neutralizing antibody to TNF-α inhibits EPO-induced proliferation of these cells.

Proliferation was measured using the MTT dye reduction assay as indicated in “Materials and methods.” (A) HCD57 (lanes 1-5) cells were deprived of EPO for 18 hours prior to addition of 1 (lane 2), 10 (lane 3), 100 (lane 4), or 1000 (lane 5) ng/mL TNF-α for 48 hours. (B) HCD57 cells were deprived of EPO overnight and then treated with EPO in the presence (lanes 3-6) or absence (lane 2) of neutralizing anti–TNF-α antibody for 48 hours. Indicated is μg/mL neutralizing antibody added. Excess TNF-α (10 ng/mL) was added to counteract the effect of the neutralizing antibody (lane 6).