IL4 and infection: For the condition that IFN-γ FC/IL-4 FC < 1 (Th2-type infections, such as HIV and EV71 infections), max FC = IFN-γ FC × (IL-4 FC/IFN-γ FC) = IL-4 FC, which means that the range of variation of IL-4 is the maximum amplitude of all cytokines.