FIG 2.

CD4-specific binding of gp120 to RA-treated human PBMCs. Biotinylated gp120 from HIV-1 isolates SF162 (subtype B) and TV-1 (subtype C) was incubated with RA-treated PBMCs at 4°C for 15 min in HEPES buffer containing Ca²⁺ and Mn²⁺. Bound gp120 was detected with PE-avidin and flow cytometry analysis. The binding of gp120 to RA-treated PBMCs preincubated with a saturating concentration (25 μg/ml) of the mouse anti-human CD4 MAb Leu3a was also measured in this assay. Assays were performed with PBMCs from three donors. Black curves in the histograms, unstained PBMCs; gray curves, PBMCs incubated with avidin-PE only; red curves, PBMCs incubated with biotinylated gp120 from the indicated HIV-1 isolate.