Figure 4. Cytokine protein levels secreted by THP-1 cells 24 hr after exposure to Al₂O₃ or carbon black nanoparticles (CB NP).

THP-1 cells were exposed to low (10 µg/ml) and high (100 µg/ml) doses of Al₂O₃ or CB NP. ELISAs were performed on cell supernatants for ELISAs were performed on cell supernatants for A) IL-1β, B) OPN, C) IL-6 and D) TNF-α. Data are representative graphs of three separate experiments and are expressed as means ± SEM. Asterisk directly above bar indicate comparison to control, whereas asterisk over connecting bar indicate comparison between CB NP and Al₂O₃ NP. *P<0.05, **P<0.01, ***P<0.001. Data are representative of three experiments and expressed as means ± SEM.