Fig. 1

Co-stimulation of epithelial cells with bacteria and virus potentiates inflammatory cytokine release. BEAS-2B cells were first exposed to heat-inactivated preparations of non-typeable (NT) H. influenzae (a, d), P. aeruginosa (b, e) or S. pneumoniae (c, f) for 4 h and subsequently infected with RSV and incubated for up to 72 h in the presence of bacteria. Concentrations of IL-6 (a–c) and IL-8 (d–f) in culture supernatants were determined by ELISA. The theoretical additive effect (dashed line) was calculated as the sum of bacteria and virus-induced cytokine secretion. Symbols indicate a statistically significant effect of bacteria alone (*), virus alone (#) and a significant interaction between bacteria and virus (&) as determined by Two Way Repeated Measures ANOVA (p < 0.05). hpi: hours post viral infection