Fig. (3) The effect of 2G12 antibody on syncytium formation between Env+ cells and SupT1 cells. The Env+ cells were incubated with the antibodies for 30 min before the addition of the SupT1 cells. The cells were then incubated for 3 h at 37°C, washed twice with PBS, and then observed by fluorescence microscopy. (A) Fluorescence micrograph of cells incubated with 10 µg/ml 2G12 antibody. (B) Inhibition of cell-cell fusion by 2G12 antibody at varying concentrations. The vertical bars indicate the spread of duplicate determinations.