HCV-immune complexes and B-cell association. HCV JFH-1 was incubated with increasing concentrations of IgG purified from healthy and HCV-infected subjects at 37°C for 1 hour. Virus-immune complexes were mixed with CD40L/IL-4–stimulated L3055–Bcl-2 cells at 37°C for 2 hours, unbound complexes were removed by washing, the cells were cocultured with Huh-7.5, and transinfection was quantified (depicted in A). The infectivity of cell-free JFH-1–immune complexes was tested by inoculating Huh-7.5 cells, and the data were expressed as FFU/mL (B). FFU per 10⁶ B cells were calculated (C). Error bars represent the SD from 3 replicate infections.