Since CD8+ T cells have been shown to play an important role in viral clearance during primary dengue (Yauch et al, 2009) while CD4+ T cells were dispensable (Yauch et al, 2010), a CD8+ T-cell depletion experiment was conducted to further evaluate the role of this cell subset during infection with WT or T209L DENV mutant. The gene discussed is CD4; the disease is dengue disease.