FIG. 3.

4c inhibits low-pH-induced polykaryon formation. HeLa cells expressing wild-type A/X-31 HA were treated with trypsin to cleave HA0, washed, and incubated in the presence of various concentrations of 4c. Then, the pH was lowered to 5.0, and the cells were incubated for 15 min at 37°C in the presence of 4c. Following syncytium formation for 3 h at 37°C in medium, the cells were fixed, stained with Giemsa, and examined by microscopy (original magnification, ×200). Representative fields are shown.