CD4 and malaria: The gradual reduction in CD4+ T cells and steady CD8+ T cells resulted in decreased CD4+/CD8+ T cell ratios in the SIV-infected animals (S, S + P and P + S), but there were significant increases in the CD4+/CD8+ T cell ratio during the acute phase of malaria in both the P and S + P groups (Additional file 1: Fig. S1C).