Recipient mice (Thy1.2+, also T-bet ZsGreen+ to prevent rejection) that had received naïve LCMV-specific (Smarta) CD4+ T cells from T-bet ZsGreen donors (Thy1.1+) were infected with LCMV Armstrong (Arm, 200 PFU) to elicit an acute viral infection. Here, CD4 is linked to viral infectious disease.