Total numbers of splenic cells (a), CD4+ T cells (b) and CD4+ T cells producing cytokines, IFN-γ (c), IL-4 (d), IL-2 (e) and IL-10 (f) during a primary infection with P. chabaudi (ER). Spleen cells taken from mice at days 13 and 28 of infection were counted as described in the materials and methods. CD4+ T cells and cytokines, IFN-γ, IL-2, IL-4 and IL-10, were enumerated by surface and intracellular staining and analysed by FACS. The values shown represent the mean and standard errors of the means from 3 to 5 mice submitted to bites by infected mosquitoes (inf. bites), injected with 105 parasitized erythrocytes (pRBC), submitted only to uninfected mosquito bites (uninfected bites) and mice not bitten or injected (naive).