CD4 and parasitic infectious disease: Figure 1 shows the estimated time to onset of parasitemia for a model in which sporozoite survival is dependent on anti-CSP antibody titres (A), and one of the following markers of cellular immunity: CSP-specific T cells expressing two or more of TNF-α, IL-2, IFN-γ or CD40L (B);, TNF-α+ CD4+ T cells (C);, IL-2+ CD4+ T cells (D);, IFN-γ+ CD4+ T cells (E);, and CD40L+ CD4+ T cells (F).