CD4 and parasitic infectious disease: In contrast, transient depletion of CD4+ T cells 4 days post-infection (d.p.i.)in Ifngr1-/- mice resulted in initial dramatic fluctuations in parasite burden, followed by a relatively stable high-level parasitemia (10–50% of RBCs infected) that was sustained for the duration of the observation window (> 300 days; Fig 1B) in the majority of mice (~60%, with ~20% eventually clearing the infection and ~20% requiring euthanasia according to established humane endpoints).