CD4 and parasitic infectious disease: In addition to this clear role of CD8+ T cells, we found a moderate dependence on CD4+ T cells: depletion of this subset significantly reduced the protective efficacy of the vaccine, but compared to control naive mice, the CD4+ T cell-depleted mice showed low levels of protective efficacy, as measured by a 1-day median delay in the time to 1% parasitemia in the blood.