IL2 and parasitic infectious disease: To identify the cytokines produced by effector and memory T cells surviving into the phase of premunition and their dependence on persistent parasitemia, we measured IFN-γ, TNF, and IL-2 production by BrdU+ T cells in the spleen using intracellular cytokine staining after BrdU labeling from day 20 to day 30 (Fig. 5C and E).