Fig. 2

Pre-exposure of cells to NT H. influenzae increases production of inflammatory cytokines upon RSV infection. 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 24 h, after which bacteria were washed away and cells were infected with RSV for up to 72 h. 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