Therefore, mice were infected with 0.17 TCID50 IAV on day 0, neutralizing antibodies specific for either IFN-γ alone or IFN-γ and IL-6 were intraperitoneally injected on day 5, followed by secondary pneumococcal infection with 1 × 106 CFU of S. pn. Here, IL6 is linked to pneumococcal infection.