Figure 3. Direct interaction with HGF increased enzyme activity of CD13 on PBT. PBT were incubated in the absence or presence of 0.5 µg/mL PMA for 24 hrs. After being washed, unstimulated PBT alone were incubated for 24 hrs, or PMA-stimulated PBT were incubated without (A) or with (B-D) HGF for 24 hrs. After incubation, PBT were harvested and cultured for 1 hr in the absence (A,B) or presence (C,D) of Bestatin (1 µg/mL or 10 µg/mL). The enzyme activity of CD13 on PBT was measured by means of CellProbe as described in MATERIALS & METHODS. Dotted lines, thin lines, and shaded histograms represent the flow cytometric profiles of CD13 enzyme activity on unstimulated PBT alone, PMA-stimulated PBT alone, and PMA-stimulated PBT co-cultured with HGF, respectively.