Effects of LPS on fluid phase uptake of peripheral blood monocytes. Peripheral blood mononuclear cells were isolated from heparinized blood of healthy volunteers using Ficoll-Hypaque density gradient centrifugation. Subsequently, the cells residing at the interface were washed, allowed to recover from isolation, stimulated for 45 minutes at 37°C and 5% CO₂ in the presence of 1 mg/mL fluorescently labeled human serum protein, and analyzed by FACS. The scatter profile was used to identify monocytes, and average fluorescence per monocyte was determined. Nonmonocyte cell populations did not accumulate significant amounts of fluorescence. The graph shows the curves from four different healthy volunteers.