To determine if IFN-γ contributed to the control of parasitemia, cohorts of WT and PD-1KO mice were infected, then rested for 15 weeks after the clearance of the primary infection and then re-infected with Pch. On day -1 and every 2–3 days, mice were given either antibodies which block IFN-γ or control rIg. The gene discussed is IFNG; the disease is parasitic infectious disease.