FIG 4.

Effect of increased IL-18BP expression on IL-18-induced IFN-γ production in primary human CD4 lymphocytes. Primary human foreskin keratinocytes stably expressing empty plasmid (pBabe), HPV16 E7, or HPV16 Δ2 E7 were treated with IFN-γ (10 ng/ml) for 8 h. Cells were washed to remove input IFN-γ and treated with fresh medium for a further 16 h. Keratinocyte supernatants were collected and added to cultures of anti-CD3/CD28-activated human CD4 lymphocytes, which were costimulated with IL-18 (20 ng/ml) for 24 h. Supernatants were harvested and levels of secreted IFN-γ measured by ELISA. Mock-treated cells and keratinocyte supernatant alone were used as controls to demonstrate absence of IFN-γ from input samples. The data represent the average from five independent experiments, and error bars indicate SD. *, P < 0.05.