Fig. (1).

Syncytium formation between Clone69TRevEnv and SupT1 cells. (A) Env^– cells that do not express gp120/gp41 did not form syncytia with SupT1 cells. (B). Env⁺ cells expressing gp120/gp41 formed syncytia with SupT1 cells in PBS. (C) Cells as in B, but observed in a different experiment. The cells were incubated with each other for 3 h at 37°C, washed twice with PBS, and then observed by fluorescence microscopy using a dual filter.