We propose that IFNγ may play a key role in: (i) the control of viral load in the draining PLN by its activation of infected macrophages/dendritic cells; (ii) controlling virus infection in the brain by its activation of microglial cells and/or the infiltrated T cells; (iii) forming a competent neutralizing antibody response by class switch; and (iv) co-activation of the IFN-I induction in the draining PLN and brain. This evidence concerns the gene IFNG and viral infectious disease.