Given MHC II and the costimulatory molecules, CD40 and CD86 were increased by OM-85, it is likely that this effect was linked with the observed increase in influenza-specific CD8+ T-cell responses (Figure 1D), although it does not necessarily explain the rapid protection against the virus, which was already apparent in the first days post-infection prior to when the CD8+ T-cell response had developed. Here, CD40 is linked to infection.