- no significant difference between CYP3A4 activity before and 7 days after vaccination but the influenza antigen-specific production of IFN-γ by lymphocytes was highly correlated with the change in ERMBT (r = -0.614, p = 0.020) thus, IFN-γ downregulates the expression/activity of CYP3A4. This evidence concerns the gene IFNG and influenza.