FIG. 7.

Effects of soluble gp120 on the binding of ¹²⁵I–SDF-1α to CXCR4. Soluble gp120 proteins were prepared in supernatants of HEK293T cells transiently transfected with the envelope expression vectors (pNL4-3env, pNL4-3env/SDF1-51, YU2env, and mock control of pME18S). The indicated dilutions of each supernatant were incubated with U87.CD4.CXCR4 cells at 4°C for 1 h. Subsequently, ¹²⁵I–SDF-1α in binding buffer was added to cells. After incubation at 4°C for 1 h, cells were washed twice and the cell-bound radioactivities were counted in a gamma counter.