Fig. 3. EGF ligand production leads to proportional receptor binding and uptake. HMECs were treated with increasing amounts of adenovirus containing TCT and ECT expression constructs. (A) At approximately 40 hours after infection, the rate of EGF appearance in the extracellular medium was measured by ELISA over a 3 hour period in either the presence (white squares/circles) or absence (black squares/circles) of 10 µg/ml EGFR-blocking antibody 225. The amount of ligand observed in the presence of 225 is considered total EGF production, whereas the difference between the presence and absence of 225 reflects the amount of EGF consumed at that production level. (B) The relationship between the amount of EGF produced and consumed at each adenovirus MOI is shown both for TCT constructs (squares) and ECT constructs (circles).