IL6 and infection: When cells were first exposed to heat-inactivated H. influenzae (Fig. 1a) or P. aeruginosa (Fig. 1b) and subsequently infected with RSV, IL-6 release was synergistically increased: Seventy-two hours after infection, experimentally determined values of IL-6 in the culture supernatants were on average increased by 56 ± 3 % (H. influenzae) or 46 ± 9 % (P. aeruginosa) compared to the sum of cytokines released by either bacteria or virus alone (indicated as bacteria + virus (theoretical), dashed line).