Figure 6.
Immunodepletion of APRIL does not affect macrophage-induced costimulation of B cells. Macrophage-conditioned culture supernatant or recombinant human APRIL were incubated for 3 hours at 4°C with constant mixing with PBS, purified rabbit anti-human APRIL IgG, or control IgG (10 μg/mL). Protein A—Sepharose beads were added for the final 90 minutes to bind immune complexes. After centrifugation at 4°C, immunodepleted supernatants were sterile filtered and cocultured with dense tonsillar B cells in the presence of anti-human IgM F(ab′)2 fragments (10 μg/mL) as described in Figure 1. The asterisk indicates statistically significant differences between samples within the bracketed groups (P < .05).
