Intracellular cytokine staining (ICS) and flow cytometry were used to evaluate the amount of IFN-γ producing CD8+ and CD4+ cells in response to VACV-specific stimulation in populations of splenocytes isolated from the spleens of mice on different days after i.n. or i.d. infection/immunization with VACV LIVP. Here, IFNG is linked to infection.