Inhibition by PJ-S21 of biotinyl-gp120 IIIB binding to peripheral blood mononuclear cells (PBMCs). HIV-1 IIIB biotinyl-gp120 (5 μg) was added to 100 μl of PBS-BSA containing graded quantities of PJ-S21. After 1 h at 20°C, the respective mixtures were added to 106 PBMCs. After 30 min the cells were washed 3× with PBS-BSA and PE-streptavidin (0.1 μg was added). Subsequently the procedures described in the legend to Fig. 6 were used. The median relative fluorescence values for control cells and cells exposed to biotinyl-gp120 in the absence and presence of PJ-S21 (100, 6.25 and 3.12 mg/ml) were 4.1, 81.31, 12.2, 35.2 and 50.0 respectively. 100 mg of PJ-S21 corresponds to ≈ 320 μg solids adsorbed from PJ onto starch.