examined serum concentrations of IFN-c and IL-4 representing Th1 and Th2 cytokines in children with influenza and found that serum levels of IFN-c and IL-4 were higher in patients with influenza A than in those with influenza B. The high ratio of IL-4 to IFN-c and the predominance of Th2 cytokine production after influenza A suggest differences in the immune response system between influenza A and B infections (Sato et al., 2009). Here, IL4 is linked to infection.